Rhubarb Cake with Butter Sauce: A Cozy Old-Fashioned Dessert

A cozy slice of Rhubarb Cake with Butter Sauce tastes like it came straight from your grandma’s kitchen. Tart, juicy rhubarb bakes into a soft, tender crumb, and then you ladle over a warm vanilla butter sauce that soaks into every bite. It’s simple, old-fashioned, and absolutely unforgettable, which is why so many classic recipes pair rhubarb cake with a rich butter or vanilla sauce for spring and summer gatherings.

In this post, we’ll walk through everything you need: a beginner-friendly recipe, step-by-step instructions, smart storage tips, and lots of ways to customize your cake so it fits your family’s taste.

This Rhubarb Cake with Butter Sauce makes a wonderful easy rhubarb dessert for potlucks, Easter brunch, or a laid-back Sunday dinner. You don’t need any fancy equipment—just a couple of bowls, a whisk, and a 9×9-inch pan.

Why You’ll Love Rhubarb Cake with Butter Sauce

If you’re new to baking with rhubarb, this is one of the easiest, most rewarding recipes to start with. Here’s why it deserves a spot in your recipe box:

1. Sweet-tart flavor balance
   Rhubarb is naturally tart, and pairing it with a buttery, vanilla-infused sauce gives you that dreamy sweet-tart contrast that makes every bite pop. Many beloved rhubarb cake recipes lean on this balance, using a simple butter or vanilla sauce to soften the tang.
2. Beginner-friendly method
   This moist rhubarb snack cake uses basic pantry staples and a straightforward creaming method. If you can measure, stir, and pour into a pan, you can make this cake. No special equipment, no complicated layers—just old fashioned rhubarb cake goodness.
3. Cozy, nostalgic texture
   The cake is soft and tender, with little pockets of juicy rhubarb. The warm vanilla butter sauce seeps into the crumb, turning each slice into a spoon-worthy treat that feels like a cross between a rhubarb coffee cake and a pudding cake.
4. Flexible for any occasion
   Serve it warm with sauce for a comforting dessert, or at room temperature as a simple spring rhubarb dessert. Add a scoop of vanilla ice cream, and suddenly you’ve got a dinner-party-worthy finale.
5. Perfect for fresh or frozen rhubarb
   While fresh rhubarb in season is wonderful, this easy rhubarb dessert also works beautifully with frozen rhubarb (with a couple of simple tweaks you’ll see below), so you can bake it year-round.
6. Endlessly adaptable
   Once you’ve made the base recipe, you can spin it into a buttermilk rhubarb cake, add a streusel like a rhubarb coffee cake, or swap in some berries. We’ll cover lots of fun twists in the Variations section.

Ingredients

Here’s everything you’ll need to make this Rhubarb Cake with Butter Sauce.

For the Rhubarb Cake

• 2 cups chopped fresh rhubarb (½-inch pieces; see notes for frozen)
• 1½ cups all-purpose flour
• 1 teaspoon baking powder
• ½ teaspoon baking soda
• ½ teaspoon fine sea salt
• 1 cup granulated sugar
• ½ cup unsalted butter, softened to room temperature
• 2 large eggs, at room temperature
• 1 teaspoon pure vanilla extract
• ½ cup buttermilk (or whole milk + 1 teaspoon lemon juice)

This combination gives you a moist rhubarb snack cake with a soft crumb and plenty of tart rhubarb in every slice. Using buttermilk echoes many classic buttermilk rhubarb cake and rhubarb coffee cake recipes, helping keep the cake tender while balancing the tang.

For the Warm Vanilla Butter Sauce

• ½ cup unsalted butter (1 stick)
• ¾ cup granulated sugar
• ½ cup heavy cream (or half-and-half)
• 1 teaspoon pure vanilla extract
• Pinch of fine sea salt (optional, for balance)

Step-by-Step Instructions

Prep:

• Preheat oven to 350°F (175°C).
• Grease a 9×9-inch pan (line with parchment if you like).

Prep rhubarb:

• Trim and wash rhubarb.
• Slice into ½-inch pieces to get 2 cups.
• If using frozen rhubarb, thaw and drain off extra liquid.

Mix dry ingredients:

• In a bowl, whisk flour, baking powder, baking soda, and salt.

Cream butter and sugar:

• In a large bowl, beat softened butter and sugar until light and fluffy (2–3 minutes).

Add eggs and vanilla:

• Beat in eggs one at a time, then add vanilla. Scrape the bowl.

Add dry ingredients and buttermilk:

• Mix in half the flour mixture.
• Add buttermilk and mix.
• Add remaining flour and mix just until combined.

Fold in rhubarb:

• Gently fold chopped rhubarb into the batter with a spatula.

Bake:

• Spread batter in pan and smooth the top.
• Bake 35–45 minutes, until golden and a toothpick comes out with a few moist crumbs.

Make butter sauce:

• In a small saucepan, melt butter.
• Stir in sugar and cream.
• Bring to a gentle boil and cook 3–4 minutes, stirring often, until slightly thickened.
• Remove from heat and stir in vanilla and a pinch of salt.

Serve:

• Let cake cool at least 15–20 minutes.
• Cut squares and serve warm with vanilla butter sauce spooned over each piece

How to Serve Rhubarb Cake with Butter Sauce

Serve this cake slightly warm, when the crumb is soft and the rhubarb is still juicy. Cut into generous squares and spoon warm butter sauce over the top so it sinks into the cake and pools on the plate.

For a fancier dessert, add a scoop of vanilla ice cream or whipped cream beside each slice. The contrast between hot cake, cold ice cream, and warm vanilla butter sauce is incredible.

At brunch, you can present it like a rhubarb coffee cake—cut into smaller squares and place on a platter with a small pitcher of sauce so guests can drizzle their own. Learn more about pairing it with other cozy cakes like French Strawberry Cake.

Fresh berries (strawberries or raspberries) and a light dusting of powdered sugar also work beautifully, especially in spring and early summer when rhubarb is in season.

How to Store Rhubarb Cake with Butter Sauce

Room temperature (short term):

• Keep the plain cake (no sauce) tightly covered at room temperature for up to 1 day.

Refrigerator:

• Store cake slices in an airtight container for 3–4 days.
• Store leftover sauce in a jar in the fridge for 3–4 days.

Freezer:

• Wrap individual slices tightly and freeze up to 3 months.
• Thaw overnight in the fridge or at room temp for a few hours.

Reheating:

• Warm cake slices in a 300°F oven for 5–10 minutes or briefly in the microwave.
• Gently reheat sauce on the stove or in the microwave, stirring often, until smooth and pourable.

For a balanced dessert rotation, discover great ideas like this bright, citrusy loaf:

• Cranberry Orange Loaf

Tips to Make Rhubarb Cake with Butter Sauce

Want your Rhubarb Cake with Butter Sauce to come out perfect every time? These practical tips will get you there:

1. Use room-temperature ingredients
   Let butter, eggs, and buttermilk sit out for 30–45 minutes before baking. Room-temperature ingredients blend more easily, giving you a smoother batter and more even crumb.
2. Measure flour correctly
   For tender cake, avoid packing flour into the cup. Fluff the flour, spoon it into your measuring cup, and level it with a knife. Too much flour is one of the most common reasons a cake turns dry instead of moist and tender.
3. Don’t overmix the batter
   Once you add the dry ingredients, mix just until the flour disappears, then fold in the rhubarb by hand. Overmixing develops gluten and can make the cake tough.
4. Handle frozen rhubarb the right way
   If you’re using frozen rhubarb, thaw it in a bowl and let excess liquid drain off naturally. Don’t squeeze it dry or your cake may end up too dense. Most high-rated rhubarb cake recipes follow this exact approach.
5. Watch the bake time closely
   Oven temperatures vary, so start checking the cake a few minutes before the suggested time. When a toothpick comes out with just a few moist crumbs and the center springs back when lightly pressed, it’s done.
6. Boil the sauce long enough—but not too long
   Boiling the butter, sugar, and cream for 3–4 minutes lets the sugar dissolve and the sauce thicken slightly. If you under-boil, the sauce may be thin and grainy; overboil and it can become too thick or caramel-like. Keep it at a gentle boil and stir often.
7. Serve the sauce warm
   Warm sauce flows over the cake and soaks in beautifully. If you make it ahead, don’t skip the step of gently reheating before serving—it’s the difference between “good” and “wow, what is this?”

Variations of Rhubarb Cake with Butter Sauce

• Streusel Rhubarb Coffee Cake:
  Top the batter with a simple streusel (flour, brown sugar, cold butter) before baking.
• Rhubarb Berry Cake:
  Swap 1 cup of rhubarb for 1 cup of chopped strawberries or raspberries.
• Brown Sugar Butter Sauce:
  Replace half or all of the white sugar in the sauce with light brown sugar for a caramel-like flavor.
• Lemon-Vanilla Twist:
  Add lemon zest to the cake batter and a splash of lemon juice to the sauce for extra brightness.
• Mini Snack Cakes:
  Bake the batter in lined muffin tins (¾ full), check at 18–20 minutes, and drizzle each with warm sauce.

FAQs

Final Thoughts

This Rhubarb Cake with Butter Sauce is the kind of recipe you keep on a card in your kitchen drawer—simple, reliable, and always loved. With its tender crumb, tart rhubarb, and warm vanilla butter sauce, it fits any season and almost any occasion.

Serve it warm, share it with people you love, and don’t be surprised when you’re asked to bring it to every gathering from now on.

Follow me on Facebook and Pinterest where I share cozy, easy-to-make baking recipes just like this Rhubarb Cake with Butter Sauce.

Rhubarb Cake with Butter Sauce

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• Author: Rosie
• Total Time: 1 hour 5 minutes
• Yield: 9 servings 1x
• Diet: Vegetarian

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Description

This Rhubarb Cake with Butter Sauce is a moist, old-fashioned rhubarb dessert topped with a warm vanilla butter sauce that soaks into every bite.

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Ingredients

Scale 1x2x3x

For the Rhubarb Cake:

• 2 cups chopped fresh rhubarb (½-inch pieces; thaw and drain if using frozen)
• 1½ cups all-purpose flour
• 1 teaspoon baking powder
• ½ teaspoon baking soda
• ½ teaspoon fine sea salt
• 1 cup granulated sugar
• ½ cup unsalted butter, softened
• 2 large eggs, room temperature
• 1 teaspoon pure vanilla extract
• ½ cup buttermilk (or whole milk + 1 teaspoon lemon juice)

For the Vanilla Butter Sauce:

• ½ cup unsalted butter
• ¾ cup granulated sugar
• ½ cup heavy cream or half-and-half
• 1 teaspoon pure vanilla extract
• Pinch of fine sea salt (optional)

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Instructions

1. Preheat oven to 350°F (175°C). Grease a 9×9-inch baking pan and line with parchment if desired.

2. Trim and wash rhubarb, then chop into ½-inch pieces to measure 2 cups. If using frozen rhubarb, thaw and drain off excess liquid.

3. In a medium bowl, whisk together flour, baking powder, baking soda, and salt.

4. In a large bowl, beat softened butter and sugar together until light and fluffy, 2–3 minutes.

5. Add eggs one at a time, beating well after each, then mix in vanilla.

6. With the mixer on low, add half of the flour mixture. Add buttermilk, then the remaining flour mixture, mixing just until combined.

7. Gently fold rhubarb into the batter. Spread batter into the prepared pan and smooth the top.

8. Bake 35–45 minutes, until golden and a toothpick inserted in the center comes out with a few moist crumbs.

9. For the sauce, melt butter in a small saucepan over medium heat, then stir in sugar and cream.

10. Bring to a gentle boil and cook 3–4 minutes, stirring often, until slightly thickened, then remove from heat and stir in vanilla and a pinch of salt.

11. Let the cake cool at least 15–20 minutes before cutting. Serve warm slices with warm vanilla butter sauce spooned over the top.

Notes

Fresh or frozen rhubarb both work; thaw and drain frozen rhubarb before using.

Do not overmix the batter once the flour is added to keep the cake tender.

For a less sweet sauce, reduce the sugar in the butter sauce to ½ cup.

The cake can be baked in a 9×13-inch pan for more servings; start checking for doneness a bit earlier.

Serve with vanilla ice cream or whipped cream for an extra-indulgent dessert.

• Prep Time: 20 minutes
• Cook Time: 45 minutes
• Category: Dessert
• Method: Baking
• Cuisine: American

Nutrition

• Serving Size: 1 slice with sauce
• Calories: 380
• Sugar: 35g
• Sodium: 220mg
• Fat: 20g
• Saturated Fat: 12g
• Unsaturated Fat: 6g
• Trans Fat: 0g
• Carbohydrates: 46g
• Fiber: 1g
• Protein: 5g
• Cholesterol: 95mg