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.
This isn’t a light, airy cake. It’s a hot water cake, which means it’s deeply moist, almost pudding-like in texture, with a tender crumb that stays soft for days. The cocoa brings richness without being too sweet, and the rhubarb adds these tart, jammy pockets throughout that keep every bite interesting.
The cream cheese frosting is tangy and light, whipped with Cool Whip for a mousse-like finish that doesn’t weigh down the cake. It’s the kind of frosting you could eat with a spoon, but somehow it works even better smeared over warm chocolate cake.
This is the cake that changes minds about rhubarb season.
Easy Chocolate Rhubarb Cake with Cream Cheese Frosting
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Kitchen Essentials
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 9×13 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
Your Own Private Notes
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.
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.Nutrition
Pairing Suggestions
This cake has enough richness and tang that it doesn’t need a heavy pairing.
A simple pour-over coffee works beautifully because the bitterness balances the sweet frosting and brings out the cocoa. If you’re going the wine route, try a late-harvest Riesling or a ruby port. Both have enough sweetness and acidity to mirror the rhubarb without competing with the chocolate. For a cocktail vibe, an espresso martini or a bourbon sour with a cherry garnish hits the right notes.
On the side, keep it minimal. Fresh whipped cream with a touch of vanilla, a scoop of vanilla bean ice cream, or even a dollop of tangy crème fraîche all work. If you want texture contrast, serve it with candied nuts or a small handful of fresh raspberries. The fruit echoes the tartness of the rhubarb and adds a pop of color to the plate.
Variations and Swaps
This cake adapts well to whatever you have on hand or whatever flavor direction you want to take it.
- Frozen rhubarb: Works just as well as fresh. Don’t thaw it first or it’ll get too watery. Dice it while frozen and toss it in. You might need an extra two to three minutes of bake time since the frozen pieces lower the batter temp slightly.
- Strawberry rhubarb version: Swap half the rhubarb for diced strawberries. The strawberries add sweetness and make the flavor more familiar if you’re serving this to rhubarb skeptics.
- Darker chocolate intensity: Use Dutch-process cocoa instead of natural cocoa for a richer, less acidic flavor. You can also fold in a half cup of mini chocolate chips for pockets of melted chocolate throughout.
- Lighter frosting option: Skip the cream cheese entirely and just whip heavy cream with powdered sugar and vanilla. It’s less tangy but lighter and lets the rhubarb shine more.
- Spiced version: Add a half teaspoon of cinnamon and a quarter teaspoon of cardamom to the dry ingredients. Both spices love rhubarb and add warmth without overpowering the chocolate.
You can also bake this in a bundt pan if you want a more dramatic presentation. Grease the pan really well and increase the bake time to 40 to 45 minutes. The frosting can be thinned with a tablespoon of milk and drizzled over the top instead of spread.
Storage Tips
Store the frosted cake covered in the fridge for up to five days.
The moisture level in this cake means it actually improves after a day or two as the flavors meld and the rhubarb softens even more. Keep it in an airtight container or cover the pan tightly with plastic wrap. Let it sit at room temperature for 15 to 20 minutes before serving so the frosting softens and the cake loses its chill.
If you’re storing unfrosted cake, wrap it tightly in plastic wrap and then foil. It’ll keep at room temperature for two days or in the fridge for up to a week. You can also freeze unfrosted cake for up to three months. Wrap individual slices in plastic wrap, then place them in a freezer bag. Thaw in the fridge overnight and frost just before serving.
The cream cheese frosting doesn’t freeze well because the whipped topping breaks down, so if you’re planning to freeze, make the frosting fresh when you’re ready to serve.
Leftover Transformations
Leftover cake is never a problem, but if you want to get creative, there are a few moves that make it feel new again.
Turn it into a trifle. Cube the cake, layer it in a glass with extra whipped cream, fresh berries, and a drizzle of chocolate sauce. It’s an instant showstopper for weekend brunch or a casual dinner party.
Make cake pops or truffles. Crumble the cake, mix it with a bit of the cream cheese frosting to bind it, roll into balls, and dip in melted chocolate. They’re rich, fudgy, and completely addictive.
Use it as a base for ice cream sundaes. Warm a slice in the microwave for 20 seconds, top with vanilla ice cream, hot fudge, and crushed nuts. The warm cake against cold ice cream is unbeatable.
Bake it into a bread pudding. Cube the cake, soak it in a mixture of eggs, cream, and a little sugar, then bake until set. It’s decadent and uses up every last crumb without feeling like leftovers.
However you use it, this cake doesn’t lose its charm after day one.
This is the kind of cake that makes rhubarb season feel like a celebration instead of a chore. The chocolate keeps it familiar, the rhubarb makes it interesting, and the hot water method guarantees you’ll never bake a dry chocolate cake again. Make it once and it’ll become your go-to for spring baking.
