The Best Lemon Chocolate Cake

This lemon chocolate cake has moist chocolate cake layers filled with tart lemon curd and frosted with tangy, silky smooth lemon Swiss meringue buttercream. This unique flavor combination is sure to impress all the chocolate and lemon lovers in your life!

Does lemon and chocolate go together? They absolutely do in this lemon chocolate cake! It's a unique combination, but trust me when I say it's a match made in heaven.

Whether you're a fan of lemon desserts, chocolate desserts, or both, this cake is sure to satisfy your sweet tooth! If you want something a little different, this lemon chocolate cake is perfect. My spicy chocolate cake is also super unique, and you should also check out this chocolate custard cake, chocolate pistachio cake, and chocolate crunch cake.

Why This Recipe Works

• Rich yet fruity flavor- The rich chocolate cake is complemented by tangy lemon curd and zesty lemon frosting for a unique and unforgettable dessert. This blueberry chocolate cake combines chocolate and fruit too!
• Simple ingredients- All the ingredients are pantry-staples or easy to find at the grocery store.
• Easy to make- Using store-bought lemon curd simplifies the baking process, making this cake quick and easy.

Key Ingredients for the Cake

• All purpose flour- Make sure to measure it correctly, ideally in grams with a kitchen scale, so your cake doesn't turn out dry.
• Cocoa powder- Use Dutch-processed cocoa powder, which is treated with alkali, making it less acidic for a richer chocolate flavor and color.
• Baking powder and baking soda- Check the expiration dates before using. If expired, the cake won't rise properly.
• Egg and egg white- An egg binds the ingredients together and an egg white gives the sponge extra lift.
• Oil- I love using oil in chocolate cakes instead of butter to make them extra moist and spongey. Use canola or vegetable oil.
• Buttermilk- Thins out the batter, adds a tangy flavor, and tenderizes the gluten for a soft, fluffy cake.
• Brewed coffee- Brings out the chocolate flavor, making it richer and deeper. Use hot coffee to bloom the cocoa powder.
• Lemon curd- Lemon curd is used to fill the cake! You can make it at home or buy it at the grocery store.
• Pasteurized egg whites- These are for the frosting and have been heat-treated to kill bacteria, so you don't have to heat them over a double boiler like in a traditional Swiss Meringue buttercream recipe. Look for them in the egg section at your grocery store and make sure the box says "pasteurized."
• Powdered sugar- By using powdered sugar, there's no need to dissolve granulated sugar in hot egg whites.
• Unsalted butter- When it comes to making buttercream, using unsalted butter gives you more control over the flavor. Make sure your butter is room temperature before you start mixing. Cold butter makes the buttercream curdle!
• Lemon juice- Use fresh lemon juice to add a tangy, bright lemon flavor to the frosting. Avoid bottled lemon juice.

See the recipe card below for quantities.

Substitutions and Variations

• Buttermilk substitute: You can substitute plain kefir, plain Greek yogurt, or sour cream for buttermilk at a 1:1 ratio. You can even make your own buttermilk by combining 1 cup of whole milk with 1 tablespoon of either vinegar or lemon juice. Just let the mixture sit for about 10 minutes and it's ready to use.
• Coffee substitute: If you don't have coffee, use hot water. The chocolate flavor won't be as deep, but you'll still have delicious cake in the end!
• Orange: Swap the lemon or orange curd, zest, and juice for a mellower citrus flavor.
• Add berries: Serve the lemon chocolate cake with fresh berries like raspberries, blueberries, or strawberries for a burst of fruity flavor.
• Cream cheese frosting: Instead of Swiss meringue buttercream, add lemon juice to this cream cheese frosting recipe.

Helpful Equipment and Tools

• I recommend using metal 6-inch round cake pans. Glass or silicone pans can cause your cake to burn! Don't forget to spray them with non-stick baking spray.
• To zest your lemons, use a microplane zester. With the zester in one hand and the lemon in the other, gently rub the lemon against the zester in one direction. Rotate the lemon as you go, and make sure only remove the yellow outer layer, not the bitter white pith underneath
• To decorate, an offset spatula and bench scraper make everything look polished and professional.

Step by Step Instructions

Preheat the oven to 350°F and line your cake pans with parchment paper.

Step 1: Stir the flour, granulated sugar, cocoa powder, baking powder, baking soda, and salt together in a large mixing bowl.

Step 2: In a separate bowl, whisk the egg, egg white, oil, buttermilk, and vanilla extract together until smooth.

Step 3: Fold the wet ingredients into the dry ingredients with a rubber spatula. There will be lots of lumps, but keep mixing until the batter drips off the spatula in ribbons.

Step 4: Pour half of the hot coffee into the cake batter and fold until smooth. Repeat with the other half; the batter will be very thin.

Step 5: Evenly distribute the cake batter between 3 cake pans and bake for 23-28 minutes or until a toothpick inserted in the center comes out clean.

Step 6: Let the cakes cool for 10 minutes, then gently flip on to a wire rack to cool completely. These cakes are soft and fragile, so be careful!

Step 7: Whisk the pasteurized egg whites and powdered sugar together in a stand mixer on low for about 30 seconds. Make sure the bowl is clean and dry; any residue will make them not whip properly.

Step 8: Increase the speed to medium-high, whipping for 8-10 minutes until you have a thick, opaque white meringue with peaks that stand up and curl on the ends.

Step 9: Add softened butter 1 tablespoon at a time, scraping down the sides of the bowl as needed. Wait for each tablespoon of butter to incorporate before adding more.

Step 10: Switch to the paddle attachment and gradually pour in the lemon juice. Don't pour it in all at once you might have a rubbery-looking mess! Keep mixing until the buttercream is smooth and doesn't taste like butter- about 10 minutes.

Step 11: Use a serrated knife or cake leveler to level the top off each cake layer, creating a flat surface. Then place one cake layer on a cake stand and spread a thin layer of buttercream evenly across it. Pipe a thick ring of buttercream around the edge and fill the center with lemon curd.

Step 12: Repeat the previous steps with the second cake layer. After that, place the last layer of cake on top with the bottom side up. Apply a thin layer of frosting all over the cake, smoothing it with an offset spatula or bench scraper to smooth it out. This is called the "crumb coat" and it helps to lock in any crumbs so they don't mix with the final layer of frosting

Step 13: Chill the cake in the freezer for 20 minutes, then generously frost with a second coat of buttercream. Pipe dollops of frosting on top of the cake or decorate with sprinkles and candied lemon slices!

Expert Baking Tips

• Don't overmix the batter. Overmixing the batter can make the cake tough and dense. Mix the ingredients until just combined.
• Use room temperature ingredients. Room temperature ingredients mix more easily and evenly. Let the eggs, butter, and buttermilk reach room temperature before using them. Pull them out of the fridge 1-2 hours before baking.
• Use a kitchen scale. Weighing the ingredients in grams yields the most accurate results! If you don't have one, measure your flour properly by spooning it into the measuring cup and leveling off. Too much flour makes cakes dry.
• Don't overbake. Check the cake a few minutes before the suggested baking time as oven temperatures can vary. The cake is done when a toothpick inserted in the center comes out clean.
• Chill the cake before decorating. Chilling the cake makes it easier to handle and prevents the frosting from melting.

Storage Tips

The chocolate lemon cake stays fresh stored in a large airtight container in the fridge for up to 1 week. If sliced, cover the cut section with extra frosting so it doesn't dry out.

Freezing Instructions

You can freeze individual cake slices or the entire by wrapping them in plastic wrap, a layer of aluminum foil, and freezing in an airtight container for up to 3 months. Thaw overnight before serving.

You can also freeze the chocolate cake layers the same way to break up the baking and decorating processes, which is helpful for prepping the cake ahead of time!

Frequently Asked Questions

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