Buttermilk Rhubarb Cake with Brown Butter & Cardamom Sauce: A Symphony of Sweet and Tangy

1. Introduction

There’s a particular joy in baking with seasonal ingredients, and rhubarb, with its striking pink stalks and distinct tangy flavor, is a springtime star. This Buttermilk Rhubarb Cake celebrates that unique tang, pairing it with a moist, tender crumb and elevating the entire experience with a luscious brown butter and cardamom sauce. It’s a cake that is both comforting and sophisticated, offering a beautiful balance of flavors and textures that feels like pure heaven in every bite.

This recipe creates a cake with a tender, moist crumb thanks to the acidity of the buttermilk, which reacts with the baking soda and also helps to tenderize the gluten. The chopped rhubarb, distributed throughout the batter, softens as the cake bakes, creating pockets of sweet-tart flavor that burst in your mouth. While a simple rhubarb cake is delightful on its own, the brown butter and cardamom sauce takes it to another level. Brown butter, with its nutty aroma and deep, caramelized flavor, adds a layer of richness, while cardamom contributes a warm, aromatic spice that complements both the brown butter and the rhubarb beautifully.

This combination of flavors is a delightful twist on traditional fruit cakes and sauces. Baking cakes with fruit and creamy or buttery sauces is a beloved dessert tradition, offering comfort and indulgence. This particular recipe highlights the elegance of brown butter and the aromatic quality of cardamom, creating a unique and memorable dessert experience. Its focus on a moist cake base and a rich sauce shares a comforting appeal with recipes featuring buttery sauces and tender baked goods, such as a Classic Boston Cream Pie Cupcake Recipe, although this recipe offers a distinct fruit and spice profile.

2. Recipe Summary

Cuisine: American / European (Dessert)

Difficulty Level: Easy to Intermediate (requires careful browning of butter)

Total Preparation and Cooking Time: Approximately 50-70 minutes (depending on pan size)

Dietary Classification: Vegetarian (contains dairy, eggs, and gluten)

3. Equipment and Utensils

You’ll need standard baking equipment and a small saucepan for the sauce:

• 9×13 inch baking pan (about 2-3 inches deep) or a 10-inch Bundt pan: The recipe provides baking times for both options. Choose the pan you prefer; a 9×13 inch pan is simpler for serving directly, while a Bundt pan offers a more decorative presentation. Ensure it’s adequately greased and floured.
• Medium bowl (about 2-quart capacity): For whisking together the dry ingredients (flour, baking powder, baking soda, salt).
• Large mixing bowl (at least 4-quart capacity): For creaming the butter and sugar and mixing the cake batter. A large bowl prevents splashing when using an electric mixer.
• Electric mixer (hand-held or stand mixer): Highly recommended for creaming the butter and sugar until light and fluffy, which is crucial for the cake’s texture.
• Measuring cups and spoons: Accuracy is essential for baking.
  • Dry measuring cups (2 cups, 1 cup, 1½ cups, ½ cup): For all-purpose flour, granulated sugar, chopped rhubarb, and packed brown sugar.
  • Liquid measuring cups (1 cup, ¼ cup): For buttermilk and heavy cream.
  • Measuring spoons (teaspoon, ½ teaspoon, ¼ teaspoon): For baking powder, baking soda, salt, vanilla extract, ground cardamom, and salt (for sauce).
• Rubber spatula or wooden spoon: For mixing, scraping down bowls, and gently folding in the rhubarb.¹
• Sharp knife & cutting board: For chopping the rhubarb.
• Small saucepan (about 1-quart capacity): For making the brown butter and cardamom sauce.
• Whisk or spoon: For stirring the sauce.
• Wire rack: For cooling the cake (especially if using a Bundt pan).
• Wooden skewer or toothpick: For testing the doneness of the cake.
• Small bowl (optional): For holding room temperature eggs and buttermilk.

4. Serving Suggestions

Buttermilk Rhubarb Cake with Brown Butter & Cardamom Sauce is a wonderfully moist and flavorful cake that is best served warm with the rich sauce poured over the top.

• Plating: Serve slices of the warm cake on dessert plates. Pour a generous amount of the warm brown butter and cardamom sauce over each slice. The warmth of the cake helps the sauce melt slightly and soak in, enhancing the moisture and flavor.
• Side Dish Ideas:
  • Vanilla ice cream: While the sauce is rich, a small scoop of vanilla ice cream is a delightful addition, creating a warm and cold contrast.
  • Whipped cream: A dollop of lightly sweetened whipped cream provides a lighter creamy element.
• Complementary Side Dishes: As a rich dessert, complementary “side dishes” aren’t typical in the savory sense. A hot cup of coffee or tea is a perfect accompaniment.
• Wine or Beverage Pairings:
  • A sweet dessert wine, like a late-harvest Riesling or a Moscato d’Asti, could complement the sweetness and fruit flavors.
  • A coffee liqueur or a spiced rum could also be served alongside.

5. Nutritional Information

Please note that the following nutritional information is an estimate per serving (based on 10-12 servings) and can vary significantly based on the exact amounts of ingredients used, particularly the butter and sugars, and the serving size. The recipe notes indicate this is an estimate.

Detailed Nutritional Breakdown (Estimate per Serving):

• Calories: Approximately 400-500 kcal
• Macronutrient Distribution (Estimate):
  • Carbohydrates: 50-60g (primarily from flour, sugars, and rhubarb)
  • Protein: 4-6g (from flour, eggs, and buttermilk)
  • Fat: 20-30g (primarily from butter, heavy cream, and eggs)
• Dietary Information: Vegetarian. Contains dairy, eggs, and gluten.
• Potential Health Benefits: Rhubarb provides Vitamin K and fiber.² Buttermilk provides calcium and protein.³ However, due to the butter, sugar, and heavy cream content, this cake is calorie-dense and high in sugar and fat. It’s best enjoyed in moderation as a treat.

6. Storage and Reheating

This cake is best enjoyed fresh and warm with the sauce, but leftovers can be stored.

• Proper Storage Instructions: Allow the cake to cool completely (if using a Bundt pan, cool before inverting). Store the cooled cake wrapped in plastic wrap or in an airtight container at room temperature for 2-3 days. Store the brown butter sauce separately in an airtight container in the refrigerator.
• Refrigeration Instructions: For longer storage of the cake (up to a week), you can refrigerate it, but the texture may become slightly drier. Store the sauce in the refrigerator for up to a week.
• Freezing Recommendations: Baked and cooled cake (without the sauce) can be frozen wrapped well in plastic wrap and then aluminum foil for up to 2-3 months. Thaw overnight in the refrigerator or at room temperature before serving with freshly made or reheated sauce. The brown butter sauce can also be frozen separately.
• Reheating Methods:
  • Cake: Individual slices of cake can be gently warmed in the microwave for 15-30 seconds.
  • Sauce: The brown butter sauce will solidify in the refrigerator. Gently reheat the sauce in a small saucepan over low heat, stirring constantly, until it is smooth and pourable again. Do not overheat.

7. Expert Tips and Variations

Make your Buttermilk Rhubarb Cake with Brown Butter & Cardamom Sauce truly heavenly with these expert tips and creative variations.

• Tips from Professional Chefs:
  • Use room temperature ingredients: As noted in the recipe, ensuring your butter, eggs, and buttermilk are at room temperature is crucial for proper creaming, emulsification, and a tender cake texture.
  • Don’t overmix the cake batter: As noted in the recipe, mix the batter on low speed just until the dry and wet ingredients are combined. Overmixing develops gluten, which can result in a tough cake.
  • Chop rhubarb into uniform pieces: Aim for roughly ½ inch pieces so the rhubarb softens and distributes evenly throughout the cake.
  • Brown the butter carefully: As noted in the recipe and tip, browning the butter is key to the sauce’s flavor. Melt the butter over medium heat and continue cooking, swirling occasionally, until it turns a deep golden brown and smells nutty. Watch constantly to prevent burning, which happens quickly.
  • Dissolve sugar in the sauce: After adding the remaining sauce ingredients to the brown butter, return to low heat and stir constantly until the brown sugar is completely dissolved and the sauce is smooth and slightly thickened, as noted in the instructions.
  • Cool cake before inverting (Bundt): If using a Bundt pan, letting the cake cool in the pan for 10-15 minutes before inverting allows it to set slightly, reducing the risk of it breaking when you turn it out.
  • Serve warm with warm sauce: The combination of warm cake and warm sauce is ideal for the best flavor experience.
• Common Mistakes to Avoid:
  • Using cold butter or eggs: Affects cake texture.
  • Overmixing the cake batter: Leads to a tough cake.
  • Burning the brown butter: Ruins the sauce flavor. Watch carefully!
  • Not dissolving sugar in the sauce: Can result in a grainy sauce.
  • Not letting Bundt cake cool slightly before inverting: Can cause the cake to break.
• Creative Recipe Variations:
  • Different spices in the sauce: As noted in the recipe note, if you don’t have cardamom, you can use cinnamon. Other warming spices like ginger, nutmeg, or a pinch of cloves could also be added to the sauce or the cake batter. The spice combination in the sauce echoes the warming spices in a Spiced Rhubarb & Ginger Bread Pudding.
  • Add other fruits to the cake: Rhubarb pairs well with strawberries, blueberries, or raspberries. You could substitute some of the rhubarb with other berries or finely diced apples, similar to variations in other rhubarb recipes.
  • Add lemon zest to the cake batter: Adding the zest of one lemon to the cake batter along with the vanilla extract would enhance the citrus notes and complement the rhubarb.
  • Add nuts to the cake: A ½ cup of chopped walnuts or pecans could be folded into the cake batter with the rhubarb for added crunch and flavor.
  • Different extract in the sauce: A tiny splash of rum extract could add another layer of flavor to the brown butter sauce.
  • Make a simple glaze: If you prefer a lighter topping instead of the brown butter sauce, you could make a simple lemon glaze (powdered sugar with lemon juice or milk) to drizzle over the cooled cake.
• Seasonal Adaptations: This cake is perfect for spring and early summer when fresh rhubarb is in season.

8. Ingredients Section

Gathering these ingredients, ensuring dairy and eggs are at room temperature, is key to a moist and flavorful cake.

• For the Buttermilk Rhubarb Cake:
  • 2 cups all-purpose flour: Standard all-purpose flour provides the structure for the cake.
  • 1 teaspoon baking powder: A leavening agent that helps the cake rise.⁴
  • ½ teaspoon baking soda: Reacts with the buttermilk to provide lift and tenderness.
  • ¼ teaspoon salt: Balances the sweetness and enhances the flavors.
  • ½ cup (1 stick) unsalted butter, softened: Unsalted butter is preferred. Ensure it is fully softened to room temperature for proper creaming.
  • 1 cup granulated sugar: Sweetens the cake.
  • 2 large eggs, room temperature: Provide richness, structure, and binding. Ensure they are at room temperature for proper emulsification.
  • 1 teaspoon vanilla extract: Enhances the sweet flavors.
  • 1 cup buttermilk, room temperature: Adds tenderness and moisture, and reacts with the baking soda.⁵ Room temperature is ideal for proper mixing.
  • 1 ½ cups rhubarb, chopped (about 3 stalks, ½ inch pieces): Washed, trimmed, and chopped into small pieces. The tartness is a key component of this cake’s flavor.
• For the Brown Butter & Cardamom Sauce:
  • ½ cup (1 stick) unsalted butter: Used for browning.
  • ½ cup brown sugar, packed: Adds sweetness and a deeper, caramel-like flavor to the sauce.
  • ¼ cup heavy cream: Adds richness and helps create a smooth sauce.
  • ½ teaspoon ground cardamom: Provides warm, aromatic spice to the sauce. As noted, cinnamon is an alternative.
  • ¼ teaspoon vanilla extract: Enhances the flavors in the sauce.
  • Pinch of salt: Balances the sweetness in the sauce.

Measurement Conversions (Approximate):

• 2 cups all-purpose flour = approx. 240g
• 1 teaspoon baking powder = approx. 4-5g
• ½ teaspoon baking soda = approx. 2-3g
• ¼ teaspoon salt (cake) = approx. 1-2g
• ½ cup (1 stick) unsalted butter, softened (cake) = approx. 113g
• 1 cup granulated sugar = approx. 200g
• 2 large eggs = approx. 100-110g
• 1 teaspoon vanilla extract (cake) = approx. 5 ml
• 1 cup buttermilk = approx. 240 ml
• 1 ½ cups rhubarb, chopped = approx. ½ – ¾ lb (225-340g)
• ½ cup (1 stick) unsalted butter (sauce) = approx. 113g
• ½ cup brown sugar, packed = approx. 100g
• ¼ cup heavy cream = approx. 60 ml
• ½ teaspoon ground cardamom = approx. 1g
• ¼ teaspoon vanilla extract (sauce) = approx. 1-2 ml
• Pinch of salt (sauce) = less than 0.5g

Quality and Sourcing Recommendations: Use fresh, firm rhubarb when in season. Ensure dairy and eggs are at room temperature for optimal cake texture.

Possible Ingredient Substitutions:

• All-purpose flour: A gluten-free all-purpose flour blend could potentially be used, but the texture might vary.
• Unsalted butter: Salted butter can be used; omit the added salt in the cake and sauce.
• Granulated sugar: A mix of granulated and brown sugar could be used in the cake batter.⁶
• Buttermilk: See Expert Tips for a homemade substitute (milk with vinegar or lemon juice).
• Rhubarb: See variations for other fruit substitutions.
• Heavy cream (sauce): Half-and-half could be used, but the sauce will be less rich.
• Ground cardamom: See note/variations for cinnamon or other spices.
• Vanilla extract (sauce): Omit if necessary.

Notes on Ingredient Preparation: Ensure butter, eggs, and buttermilk are at room temperature. Whisk dry ingredients together. Cream butter and sugar until light and fluffy. Chop rhubarb into ½ inch pieces.

9. Step-by-Step Instructions

Baking this Buttermilk Rhubarb Cake and making the brown butter sauce is a straightforward process. Follow these steps for a pure heaven dessert.

1. Preheat and Prepare:
   • Preheat your oven to 350°F (175°C).⁷
   • Grease and flour a 9×13 inch baking pan or a 10-inch Bundt pan. Ensuring the pan is well-greased and floured helps prevent the cake from sticking.
2. Dry Ingredients:
   • In a medium bowl (about 2-quart capacity), whisk together the 2 cups of all-purpose flour, 1 teaspoon of baking powder, ½ teaspoon of baking soda, and ¼ teaspoon of salt. Whisk until well combined.
3. Cream Butter and Sugar:
   • In a large mixing bowl (at least 4-quart capacity), cream together the ½ cup of softened unsalted butter and 1 cup of granulated sugar with an electric mixer. Beat on medium-high speed for 2-3 minutes, scraping down the sides of the bowl as needed, until the mixture is light, fluffy, and pale in color. This creaming process is crucial for incorporating air into the batter, which contributes to the cake’s texture.⁸
4. Add Eggs and Vanilla:
   • Beat in the 2 large eggs one at a time into the creamed butter and sugar mixture, mixing on medium speed just until each egg is incorporated before adding the next.
   • Stir in the 1 teaspoon of vanilla extract.
5. Alternate Dry and Wet Ingredients:
   • With the electric mixer on low speed, gradually add the dry ingredients (from the medium bowl) to the wet ingredients in the large bowl, alternating with the 1 cup of buttermilk.⁹ Begin and end with the dry ingredients.
   • Add about a third of the dry ingredients, mix on low speed just until partially combined.
   • Add about half of the buttermilk, mix on low speed just until partially combined.
   • Repeat with another third of the dry ingredients, the remaining buttermilk, and finally the remaining dry ingredients.
   • Mix on low speed just until the batter is combined and no dry streaks of flour remain. Do not overmix, as this can result in a tough cake. Use a spatula to scrape down the sides and bottom of the bowl to ensure everything is incorporated.
6. Fold in Rhubarb:
   • Add the 1 ½ cups of chopped rhubarb to the cake batter.
   • Use a rubber spatula to gently fold the chopped rhubarb into the batter until it is just evenly distributed. Be careful not to overmix.
7. Bake:
   • Pour the batter into the prepared baking pan (9×13 inch or Bundt). Spread the top evenly with a spatula.
   • Place the pan in the preheated oven (350°F / 175°C).¹⁰
   • Bake for 30-40 minutes if using a 9×13 inch pan, or 40-50 minutes if using a 10-inch Bundt pan. The baking time will vary depending on your oven and the pan size.
   • The cake is done when it is golden brown on top and a wooden skewer or toothpick inserted into the center of the cake comes out clean.
8. Cool:
   • Once baked, carefully remove the cake from the oven.
   • If using a 9×13 inch pan, let the cake cool in the pan on a wire rack. You can serve it directly from this pan.
   • If using a Bundt pan, let the cake cool in the pan on a wire rack for 10-15 minutes before carefully inverting it onto the wire rack to cool completely.
9. Make the Brown Butter Sauce:
   • While the cake is cooling (or after you’ve inverted it), make the sauce. In a small saucepan (about 1-quart capacity), melt the ½ cup (1 stick) of unsalted butter over medium heat.
   • Continue cooking the butter, swirling the pan occasionally, for about 5-7 minutes. Watch carefully as it cooks. The butter will foam, then the milk solids at the bottom will turn a deep golden brown, and the butter will develop a nutty aroma.¹¹ This is brown butter. Watch carefully to prevent burning.
   • Once the butter is browned, remove the saucepan from the heat immediately to stop the cooking process.¹²
   • Stir in the ½ cup of packed brown sugar, ¼ cup of heavy cream, ½ teaspoon of ground cardamom (or cinnamon, as noted), ¼ teaspoon of vanilla extract, and a pinch of salt into the brown butter.
   • Return the saucepan to low heat and cook, stirring constantly with a whisk or spoon, until the brown sugar is completely dissolved and the sauce is smooth and slightly thickened. This should take about 1-2 minutes.
   • The sauce will thicken slightly as it cools, as noted in the recipe note. If it becomes too thick to pour easily, you can gently reheat it before serving.
10. Serve:
    • Pour the warm brown butter and cardamom sauce generously over the cooled cake (either in the 9×13 inch pan or over the inverted Bundt cake on the wire rack or serving plate).
    • Slice the cake and serve warm, with extra sauce on the side if desired.

Visual Baking and Preparation Cues:

• Creamed butter and sugar: Light, fluffy, and pale.
• Cake batter: Combined ingredients with visible rhubarb folded in.
• Baked cake: Golden brown top, passes the skewer test.
• Brown butter: Deep golden brown color with nutty aroma.
• Sauce: Smooth, slightly thickened, with no grainy sugar.

Possible Troubleshooting Tips:

• Cake is tough: Usually due to overmixing the batter after adding the dry ingredients. Mix just until combined.
• Cake is dry: Usually due to overbaking. Ensure you test for doneness at the earlier end of the time range.
• Bundt cake stuck to the pan: Ensure the pan was very well greased and floured. Letting it cool slightly before inverting is also crucial.
• Brown butter burned: If the milk solids turn black and the butter smells acrid, it’s burned and you’ll need to start the sauce again. Watch carefully during browning.
• Sauce is grainy: Ensure the brown sugar is completely dissolved by stirring constantly over low heat after adding the other ingredients.
• Rhubarb sank to the bottom: This can happen if the rhubarb pieces are too large or if the batter is too thin. Ensure pieces are about ½ inch and batter is not overmixed.

Explanation of Cooking Methods:

• Creaming: Beating butter and sugar incorporates air, contributing to the cake’s rise and tender texture.¹³
• Emulsification: Adding eggs to the creamed mixture helps bind fat and liquid, creating a smooth batter.¹⁴
• Alternating Wet and Dry Ingredients: This method helps create a tender crumb by preventing overdevelopment of gluten.
• Folding: Gently incorporating delicate ingredients like rhubarb without crushing them or overmixing the batter.
• Baking: The heat of the oven activates leavening agents, causes the batter to rise, and sets the structure of the cake, while the rhubarb softens.
• Browning Butter: Cooking butter past the melting point caramelizes the milk solids, creating a nutty aroma and deep flavor.¹⁵
• Simmering (Sauce): Heating the brown butter with other ingredients dissolves the sugar and creates a smooth, pourable sauce.
• Cooling: Allows the cake to set after baking.

10. Frequently Asked Questions (FAQ)

Here are some common questions about making Buttermilk Rhubarb Cake with Brown Butter¹⁶ & Cardamom Sauce:

• Do I have to use buttermilk? Buttermilk is important for this recipe as its acidity reacts with the baking soda for leavening and contributes to the cake’s tenderness. If you don’t have buttermilk, you can make a substitute by adding 1 tablespoon of white vinegar or lemon juice to 1 cup of milk and letting it sit for 5-10 minutes until it curdles.¹⁷
• Can I use frozen rhubarb? Yes, you can use frozen rhubarb. Do not thaw it before chopping and adding to the batter; gently fold in the frozen pieces. The baking time might be slightly longer.
• Is browning the butter difficult? Browning butter requires attention, but it’s not difficult. The key is to watch it constantly after it melts and swirls, stirring or swirling occasionally, until the milk solids at the bottom turn golden brown and it smells nutty. Remove it from the heat immediately when it reaches the desired color to prevent burning.
• Can I use cinnamon instead of cardamom in the sauce? Yes, as noted in the recipe note, cinnamon is a good substitute for cardamom and will provide a different but still delicious warming spice flavor in the sauce.¹⁸
• What is the texture of the cake like? The cake is designed to be moist and tender, with a soft crumb and pockets of tangy, softened rhubarb throughout. The brown butter sauce adds extra moisture and richness.
• Can I make this into cupcakes? While the flavors would work, this recipe is specifically developed for a 9×13 inch or Bundt pan. Adapting it to cupcakes would require adjusting baking time (likely significantly shorter) and potentially batter quantity. For cupcakes, consider a recipe specifically designed for those, like Raspberry Lemon Heaven Cupcakes.
• How long does the brown butter sauce last? Stored in an airtight container in the refrigerator, the brown butter sauce will last for up to a week. It will solidify when chilled and needs to be gently reheated before serving.

This Buttermilk Rhubarb Cake with Brown Butter & Cardamom Sauce is a moist, tender, and incredibly flavorful dessert that celebrates the unique tang of rhubarb and the richness of brown butter. It’s a pure heaven dessert that’s perfect for any occasion. Enjoy baking and savoring this delightful cake!