Easy Chocolate Rhubarb Cake with Cream Cheese Frosting

Chocolate Rhubarb Cake with Cream Cheese Frosting is a surprisingly delicious combination. If you think chocolate and rhubarb don't belong together, you're missing out on one of the best unlikely dessert pairings.

Prep Time20

Cook Time25

Total Time45

Course: Dessert

Cuisine: American

Keyword: cake recipe, chocolate Recipe, easy recipe, fruit recipe, summer dessert

Servings: Servings, 9 X 13 pan

Calories: 265kcal

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Kitchen Essentials

Aluminum Cake Pan

Country Bowls

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

Hot water cakes are forgiving, but timing matters once you add the liquid.
Start by whisking together your dry ingredients in a large bowl: flour, sugar, cocoa powder, baking soda, baking powder, and salt. Make sure everything is evenly distributed so you don't get pockets of baking soda or cocoa clumps later.
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
In a separate bowl, whisk the melted butter, eggs, and warm water until smooth and slightly frothy. Add the vanilla. This is your liquid base, and it should feel thin, almost soupy. That's exactly what you want. For the warm water, aim for a bath water temperature about 100°F to 110°F (38°C to 43°C).
2 Large Eggs, ½ Cup Butter, 1 3/4 Cup Warm Water, 1 Teaspoons Vanilla
Pour the wet into the dry and beat immediately. Do not walk away. Do not add the wet and then prep your rhubarb. The reaction between the warm water and the leavening agents starts working the second they meet, so you need to beat this batter for at least a minute until it's smooth and starts to look slightly puffed. If you let it sit, you lose lift. Once the batter is glossy and combined, fold in the finely diced rhubarb. Don't overmix here, just get it incorporated.
2 Cups Rhubarb
Pour the batter into a greased 9x13 pan and smooth the top. It'll look thin, almost pourable. That's normal. Slide it into a 350-degree oven and bake for 25 to 30 minutes. Start checking at 25. You're looking for a cake that springs back lightly when touched and a knife that comes out with just a few moist crumbs, not wet batter.
While the cake cools completely, beat the cream cheese and powdered sugar together until smooth and fluffy, then fold in the whipped topping. Don't overbeat once the Cool Whip is in or it'll deflate. Spread the frosting over the cooled cake and hit it with chocolate sprinkles if you're feeling it. The frosting should be thick enough to hold peaks but soft enough to spread without tearing the cake.
8 Ounces Cream Cheese, ½ Cup Powdered Sugar, 8 Ounces Whipped Topping, Chocolate Sprinkles

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Notes

How to Know It's Done

The visual cues matter more than the timer with this cake.

You want the surface to look set and matte, not shiny or wet. When you lightly press the center with your finger, it should spring back slowly but not leave an indent. If it sinks and stays down, give it another three to five minutes. The edges will start to pull away from the pan just slightly, maybe a quarter inch, and you'll see a tiny gap forming. That's your signal that the structure has set.

Knife test: Insert a thin knife or toothpick into the center. You want moist crumbs clinging to it, not wet batter. If it comes out completely clean, you've overbaked it and the texture will be drier than ideal.
Smell: You'll notice the chocolate aroma intensifies and loses that raw flour smell. It gets deeper, almost fudgy.
Color shift: The batter goes from glossy dark brown to a more muted, matte finish across the top.

Because this is a hot water cake, it stays moist longer than traditional cakes, so erring on the side of slightly underdone is better than overbaking. The residual heat continues to cook it even after you pull it from the oven.

Tips from the Pros

Professional bakers treat hot water cakes differently than standard layer cakes, and for good reason.

Always use warm water, not hot. If the water is too hot, it can start cooking the eggs when you whisk everything together, and you'll end up with scrambled bits in your batter. Aim for water that's warm to the touch but not steaming. Around 110 to 120 degrees is perfect. If you don't have a thermometer, think baby bottle warm.

Dice the rhubarb small and consistent. Big chunks release too much moisture and create soggy pockets. You want pieces no bigger than a quarter inch so they distribute evenly and soften into the cake without turning mushy. If your rhubarb is especially thick, split the stalks lengthwise before dicing.

Don't skip the beating step after adding wet to dry. This is where the texture is built. The longer you beat (within reason, about 60 to 90 seconds), the more air you incorporate, and the lighter the crumb becomes despite the dense batter. Use a hand mixer or stand mixer on medium speed. Stirring by hand won't give you the same lift.

Let the frosting ingredients come to room temperature before mixing. Cold cream cheese doesn't blend smoothly and you'll end up with lumps. If you're short on time, microwave the cream cheese for 10 seconds at a time until it's soft but not melted. The whipped topping should also be thawed completely or it won't fold in without deflating.

If you're making this ahead, frost it the day you plan to serve it. The frosting holds up in the fridge, but it tastes best when it's had a chance to sit at room temp for about 20 minutes before serving so it softens and gets creamy again.

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