One-Bowl Chocolate Anniversary Cake

This one-bowl chocolate anniversary cake is the one I turn to for every celebration. The crumb is tender and deeply chocolaty, and it comes together with simple pantry ingredients without ever pulling out a stand mixer.

A single bowl, a whisk, and a few minutes of stirring is all you need before the layers hit the oven. No melting chocolate separately, no fussy steps, just a straightforward cake that bakes up tall and dark.

What Makes This Cake So Good

The crumb is velvety and almost fudge-like, with a clean cocoa flavor that stays rich but never bitter. A splash of hot coffee in the batter wakes up the chocolate without adding any coffee taste.

I love that the same bowl makes both the cake and a quick chocolate buttercream. You get two full layers ready for a special evening with very little extra effort.

Ingredients

• 2 cups (250 g) all-purpose flour: spooned and leveled, not scooped
• 1 ¾ cups (350 g) granulated sugar
• ¾ cup (65 g) unsweetened cocoa powder: natural or Dutch-process both work
• 2 tsp baking powder
• 1 tsp baking soda
• 1 tsp fine sea salt
• 1 cup (240 ml) buttermilk: if you only have milk, stir in 1 tbsp lemon juice and let it sit 5 minutes
• ½ cup (120 ml) neutral oil: canola, vegetable, or grapeseed
• 2 large eggs: at room temperature
• 2 tsp vanilla extract
• ½ cup (120 ml) hot brewed coffee: or hot water for a milder chocolate note

For the frosting

• 1 cup (230 g) unsalted butter: softened to room temperature
• 3 cups (360 g) powdered sugar
• ½ cup (45 g) unsweetened cocoa powder
• 3 tbsp milk: plus more if needed
• 1 tsp vanilla extract
• pinch of salt

Variations / Substitutions

• No buttermilk?: Stir 1 tbsp white vinegar or lemon juice into 1 cup milk and let it sit 5 minutes before using.
• Oil swap: Any neutral oil works well; melted coconut oil is fine too, but the cake will taste slightly sweeter.
• Dairy-free: Use a plant-based milk with 1 tbsp vinegar for the buttermilk, and swap the butter for a good vegan stick butter in the frosting.
• Deeper chocolate: Replace the hot water in the batter with hot dark coffee or espresso for an even richer note.
• Different frosting: A simple chocolate ganache or cream cheese frosting also pairs beautifully. For a lighter option, try the vanilla buttercream from my Classic Vanilla Cake recipe.

How To Make One-Bowl Chocolate Anniversary Cake

Step 1: Mix the Dry Ingredients

Heat your oven to 350°F (175°C). Grease two 8-inch round cake pans and line the bottoms with parchment. In a large bowl, whisk together the 2 cups flour, 1 ¾ cups sugar, ¾ cup cocoa powder, 2 tsp baking powder, 1 tsp baking soda, and 1 tsp salt until no streaks of cocoa remain.

The mixture will look uniform and smell faintly of chocolate. A quick whisk here keeps the leavening even so the cake rises smoothly.

Step 2: Whisk in the Wet Ingredients

Pour in the 1 cup buttermilk, ½ cup oil, the 2 eggs, and 2 tsp vanilla. Whisk until the batter is just combined and glossy. You will still see a few small lumps, and that is fine. Pour in the ½ cup hot coffee and whisk again, gently, just until the batter is fluid and smooth.

The batter will be thin, like glossy chocolate syrup. This thin consistency is what gives the cake its soft, tender crumb after baking.

Step 3: Bake the Layers

Divide the batter evenly between the prepared pans. Bake on the middle rack for 28 to 32 minutes, until the tops spring back when lightly pressed and a toothpick inserted in the center comes out with a few moist crumbs.

The kitchen will smell warm and toasty. Let the layers cool in the pans on a rack for 10 minutes, then run a knife around the edges and turn them out onto the rack to cool completely. Warm layers will melt the frosting, so do not rush this step.

Step 4: Whip the Frosting

While the cakes cool, beat the 1 cup softened butter with an electric mixer until creamy, about 1 minute. Add the 3 cups powdered sugar, ½ cup cocoa powder, 3 tbsp milk, 1 tsp vanilla, and a pinch of salt. Start mixing on low to avoid a sugar cloud, then increase speed and beat until fluffy, about 2 minutes. If the frosting feels too stiff, add another tablespoon of milk.

You should end up with a spreadable, mousse-like frosting that holds its shape but still moves smoothly under a spatula.

Step 5: Frost and Serve

Place one cooled cake layer on a serving plate, flat side up. Spread about a third of the frosting over the top, right to the edges. Set the second layer on top, flat side down, and pile the remaining frosting onto the center. Work it outward and down the sides in a thin, even layer. Slice and serve right away, or chill for 20 minutes for cleaner cuts.

A Few Notes Before You Start

• Bring your eggs and buttermilk to room temperature while you gather everything else. Cold ingredients can make the batter seize slightly and affect rise.
• Do not overmix once the wet ingredients are in. A few small flour streaks in the batter are safer than a dense, tough cake.
• Check the cakes at the 28-minute mark. Every oven runs a little differently, and pulling them a minute early is better than overbaking.
• If the tops dome, a serrated knife can level them while still slightly warm for an even stack.
• The frosting can be made a day ahead. Store it covered in the fridge, then let it soften at room temperature and re-whip briefly before using.

Bake times by pan:

Storing Leftovers

• Refrigerate: Cover the frosted cake and refrigerate for up to 5 days. The cake stays moist.
• Reheating: Serve slices at room temperature, not cold, so the frosting softens. A quick 15-minute rest on the counter does the trick.
• Freeze: Wrap unfrosted layers tightly in plastic and freeze for up to 2 months. Thaw at room temperature, then frost as usual.

Frequently Asked Questions

Can I skip the coffee in the cake?

You can use hot water instead. The coffee does not add a coffee flavor, just deepens the chocolate, but hot water works just fine.

Why did my cake sink in the middle?

Usually that means the oven door was opened too early, the batter was overmixed, or the cake needed a few more minutes. Once the oven is on, try not to peek before the 25-minute mark.

Can I use butter instead of oil in the cake?

Oil gives this cake its reliably soft texture and keeps it moist longer. Melted butter will work, but the crumb will be slightly denser and will dry out a bit faster.

How far ahead can I make the layers?

The baked layers can be cooled, wrapped, and kept at room temperature for a day, or frozen for up to 2 months. Frost the day you plan to serve for the freshest look.

Chocolate Anniversary Cake Recipe

Print Recipe Pin Recipe

Prep Time 15 minutes mins

Cook Time 30 minutes mins

Total Time 45 minutes mins

Servings: 12 servings

Calories: 478

Ingredients Method Notes

Ingredients

  

• 2 cups (250 g) all-purpose flour
• 1 ¾ cups (350 g) granulated sugar
• ¾ cup (65 g) unsweetened cocoa powder
• 2 tsp baking powder
• 1 tsp baking soda
• 1 tsp fine sea salt
• 1 cup (240 ml) buttermilk
• ½ cup (120 ml) neutral oil
• 2 large eggs
• 2 tsp vanilla extract
• ½ cup (120 ml) hot brewed coffee

Method

 

1. Heat oven to 350°F (175°C). Grease two 8-inch round pans and line with parchment. Whisk flour, sugar, cocoa, baking powder, baking soda, and salt in a large bowl until combined.
2. Add buttermilk, oil, eggs, and vanilla. Whisk until just combined. Stir in hot coffee until the batter is smooth and thin.
3. Divide batter between pans. Bake 28 to 32 minutes, until tops spring back. Cool in pans 10 minutes, then turn out onto a rack to cool completely.
4. For the frosting, beat butter until creamy. Add powdered sugar, cocoa, 3 tbsp milk, vanilla, and salt. Beat until fluffy, adding more milk if needed.
5. Place one layer flat side up on a plate, spread with a third of the frosting. Add second layer flat side down, frost top and sides. Slice and serve.

Notes

Let the cake layers cool completely before frosting. For the neatest slices, chill the frosted cake 20 minutes, then wipe the knife between cuts.