If you’re looking for a delicious new way to use fresh rhubarb, this Chocolate Rhubarb Cake is a must-try. The combination may sound unusual at first, but the tartness of rhubarb perfectly balances the rich chocolate flavor, creating a moist and tender cake that’s not overly sweet.
Made using the classic hot water cake method, this easy sheet cake develops a soft crumb and deep chocolate flavor while staying wonderfully moist. Finished with a light cream cheese frosting and a sprinkle of chocolate sprinkles, it’s a crowd-pleasing dessert that’s perfect for potlucks, family gatherings, holidays, or simply enjoying with a cup of coffee.
Whether you’re harvesting rhubarb from the garden or picking up a few stalks at the farmers market, this chocolate rhubarb cake is a delicious way to celebrate the season.
Why You’ll Love This Recipe
- Easy one-pan dessert baked in a 9×13-inch pan.
- A wonderful balance of rich chocolate and tangy rhubarb.
- Moist texture thanks to the hot water cake method.
- Simple ingredients you may already have on hand.
- Perfect for spring and early summer rhubarb season.
- Light cream cheese frosting complements the chocolate beautifully.
What Does Rhubarb Taste Like with Chocolate?
Rhubarb has a naturally tart flavor that helps cut through the richness of chocolate. Similar to how raspberries pair well with chocolate, rhubarb adds a subtle tanginess that keeps each bite balanced and flavorful. As the cake bakes, the rhubarb softens and blends into the chocolate cake, creating pockets of moisture and bright flavor throughout.
Chocolate Rhubarb Cake with Cream Cheese Frosting
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Equipment
Ingredients
Hot Water Cake Ingredients
- 2 1/2 Cups All-Purpose Flour
- 1 Teaspoons Baking Soda
- 1 Cups Granulated Sugar
- 1/3 Cup Unsweetened Cocoa Powder
- 2 Teaspoons Baking Powder
- 1 Teaspoon Salt
- 2 Cups Rhubarb finely diced
- 2 Large Eggs
- ½ Cup Butter 1 stick melted and cooled a bit
- 1 3/4 Cup Warm Water 100°F to 110°F (38°C to 43°C)
- 1 Teaspoons Vanilla
Cream Cheese Frosting
- 8 Ounces Cream Cheese 1 block at room temperature
- ½ Cup Powdered Sugar
- 8 Ounces Whipped Topping 1 container
Garnish
- Chocolate Sprinkles
Instructions
How to Make Chocolate Rhubarb Cake
- Preheat your oven to 350 degrees Fahrenheit. Grease a 9×13-inch baking pan.
- Combine the Dry Ingredients. In a large mixing bowl, stir together the flour, baking soda, sugar, cocoa powder, baking powder, and salt.2 1/2 Cups All-Purpose Flour, 1 Teaspoons Baking Soda, 1 Cups Granulated Sugar, 1/3 Cup Unsweetened Cocoa Powder, 2 Teaspoons Baking Powder, 1 Teaspoon Salt
- Mix the Wet Ingredients. In a separate bowl, whisk together the eggs, melted butter, warm water, and vanilla extract until smooth. A good target temperature for the water is about 100°F to 110°F (38°C to 43°C)—similar to warm bath water.2 Large Eggs, ½ Cup Butter, 1 3/4 Cup Warm Water, 1 Teaspoons Vanilla
- Make the Batter. Pour the wet ingredients into the dry ingredients and immediately beat until smooth. The batter should become light and slightly puffy.
- Important: With hot water cakes, the wet ingredients should be mixed into the dry ingredients and beaten right away. Have everything ready before combining the ingredients for the best texture.
- Add the Rhubarb. Fold the finely diced rhubarb into the batter until evenly distributed.2 Cups Rhubarb
- Pour the batter into the prepared baking pan and spread evenly.
- Bake for approximately 30 minutes, beginning to check for doneness at 25 minutes. A knife or toothpick inserted into the center should come out clean or with only a few moist crumbs attached.
- Allow the cake to cool completely before frosting.
Make the Cream Cheese Frosting
- In a medium bowl, beat the softened cream cheese and powdered sugar together until smooth and creamy.8 Ounces Cream Cheese, ½ Cup Powdered Sugar
- Gently fold in the whipped topping until fully combined and fluffy.8 Ounces Whipped Topping
- Spread evenly over the cooled cake.
- Top with chocolate sprinkles if desired.Chocolate Sprinkles
Notes
Tips for Success
- Dice the rhubarb finely so it distributes evenly throughout the cake.
- Allow the melted butter to cool slightly before adding it to the eggs.
- Use warm water, not hot boiling water.
- Frost only after the cake has completely cooled.
- For clean slices, chill the frosted cake for 20 to 30 minutes before serving.
What Is a Hot Water Cake?
This Chocolate Rhubarb Cake uses a variation of the classic hot water cake method. Instead of relying on milk, the batter is made with warm water, which helps create a cake that is exceptionally moist, tender, and light.
When the warm liquid is mixed into the cocoa powder and dry ingredients, it helps dissolve the cocoa more completely, bringing out a deeper chocolate flavor. The batter also becomes smooth and airy, helping the cake bake up with a soft crumb and delicate texture.
The result is a chocolate cake that stays moist for several days without becoming heavy or dense.
Why Use Warm Water Instead of Cold Water?
Warm water blends more easily with the cocoa powder and other ingredients, creating a smoother batter with fewer lumps. It also helps the sugar dissolve more readily, contributing to an even texture throughout the cake.
For this recipe, the water should feel comfortably warm to the touch but not hot. If the water is too hot, it can begin cooking the eggs when the wet ingredients are mixed together.
A good target temperature is about 100°F to 110°F (38°C to 43°C)—similar to warm bath water.
Benefits of the Hot Water Cake Method
- Produces a moist and tender cake crumb.
- Enhances the chocolate flavor of the cocoa powder.
- Creates a smooth batter that mixes easily.
- Helps the cake stay soft for days after baking.
- Uses simple pantry ingredients without the need for milk.
Storage
Whether you’re making this cake ahead for a gathering or saving leftovers for later, proper storage will help keep it moist and delicious.
Refrigerator
Because of the cream cheese frosting, store the cake covered in the refrigerator for up to 4 days.
Freezer
The unfrosted cake freezes well. Wrap tightly in plastic wrap and aluminum foil and freeze for up to 3 months. Thaw overnight in the refrigerator before frosting and serving.
With its tender crumb and creamy frosting, this cake stores surprisingly well, making it a great make-ahead dessert for busy weeks and special occasions alike.
Variations
One of the best things about this chocolate rhubarb cake is how easy it is to customize. Here are a few simple ways to make it your own.
Add Chocolate Chips
Fold 1 cup of semi-sweet chocolate chips into the batter for even more chocolate flavor.
Use a Chocolate Glaze
Instead of cream cheese frosting, drizzle the cooled cake with a simple chocolate glaze.
Add Nuts
Chopped walnuts or pecans add a pleasant crunch and pair well with both chocolate and rhubarb.
Don’t be afraid to experiment with your favorite mix-ins and toppings. This versatile cake recipe is a wonderful base for creating new family favorites.
Can I use frozen rhubarb?
Yes. Thaw the rhubarb first and drain away excess liquid before adding it to the batter.
Do I need to peel rhubarb?
No. Simply wash the stalks well and trim the ends before dicing.
Why is warm water used in this cake?
Warm water helps dissolve ingredients more thoroughly and intensifies the cocoa flavor, resulting in a moist cake with a soft crumb.
Can I make this cake ahead of time?
Absolutely. The cake can be baked a day in advance and stored covered. Frost just before serving or keep refrigerated until needed.
This Chocolate Rhubarb Cake is proof that rhubarb isn’t just for pies and crisps. The tart rhubarb adds a wonderful brightness to the rich chocolate cake, while the fluffy cream cheese frosting brings everything together in every delicious bite. It’s an easy dessert that feels a little unexpected and special without requiring any fancy ingredients.
Whether you’re baking with rhubarb fresh from the garden or taking advantage of the season at your local market, this cake is a wonderful way to enjoy one of spring’s most beloved harvests. I hope it becomes a favorite in your kitchen too.
This one is going on the annual rhubarb recipe rotation.