The Best Marble Loaf Cake with Peanut Butter Buttercream

The most delicious Marble Loaf Cake with swirls of tender and moist yellow cake and chocolate cake, topped with a peanut butter buttercream.

Marble Loaf Cake

A few years ago, my son requested a marble cake with peanut butter buttercream for his birthday. The combination of chocolate and yellow cake with the nutty, smooth buttercream was utterly delicious.

As I planned my new cookbook, I knew this was a recipe I wanted to include, but I also knew it needed to be simplified in two ways: the method and the execution.

Rather than make two separate batter recipes, I created a recipe that is equally delicious, moist, and flavorful, but only requires you to make one batter. I also turned it into a loaf cake simply to make your life easier 🙂

Don’t worry – you can absolutely use this recipe as a layered cake. Just check out my tips at the bottom of the post.

How to Turn the Marble Loaf Cake Into a Layered Cake

To turn this Marble Loaf Cake recipe into a layered cake, follow these easy steps:

• Double the recipe – you’ll follow the recipe exactly as written but with 2x the amount of ingredients so you can fill two 8-inch cake layers.
• Temperature stays the same – the oven temperature will stay the same for all of my cakes, whether they are loaf cakes, layered cakes, sheet cakes or cupcakes.
• Decrease the baking time – the one thing you will change is the amount of time the cakes are baking for. Instead of 45 to 50 minutes for the loaf pan, you’ll bake two 8-inch cake pans for 35 to 40 minutes. If you want to make this a three layered cake with three 8-inch cake pans, the bake time will be closer to 25 to 30 minutes. Remember, the cake layers are done when a toothpick inserted in the center of the cake comes out with a few moist crumbs on it.

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Marble Loaf Cake with Peanut Butter Buttercream

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Ingredients

  

For the Cake

• 1 ⅓ cups 266.7 g granulated sugar, divided
• ⅓ cup water
• ⅓ cup cocoa powder
• 2 ounces unsweetened dark chocolate
• 1 ⅔ cups 191.6 g cake flour
• 1 teaspoon 4 g baking powder
• ½ teaspoon 3 g salt
• ½ cup 113 g unsalted butter, at room temperature
• 3 eggs at room temperature
• ½ teaspoon 2.1 g vanilla extract
• ½ cup 120 g buttermilk, at room temperature

For the Buttercream

• 2 cups 250 g powdered sugar, measured then sifted
• ½ cups 113 g unsalted butter, slightly cold
• ¼ cup 62.5 g creamy peanut butter
• 1 teaspoon 4.2 g pure vanilla extract
• 2 tablespoons 30 g heavy whipping cream
• Pinch of salt

Instructions

 

FOR THE CAKE

• Preheat your oven to 325 degrees F. Spray a 9×5-inch loaf pan with nonstick spray. Line the pan with parchment paper, allowing the parchment to come up the sides of the pan. Spray the parchment. Set aside.
• In a small saucepan, combine ⅓ cup sugar, the water, cocoa powder, and chocolate. Stir over medium heat until the chocolate is melted and the mixture is smooth. Remove from heat and let cool while you make the cake batter.
• In a medium size mixing bowl, whisk together the flour, baking powder, and salt. Set aside.
• In the bowl of a stand mixer fitted with the paddle attachment, beat the butter and remaining sugar on medium speed until light in color and fluffy in texture, about 2 to 3 minutes.
• Add the eggs, one at a time, making sure to scrape down the sides and bottom of the bowl in between additions. Stir in the vanilla extract.
• Continue to beat on medium-high speed for about 2 minutes, until the mixture gets smooth in texture and slightly bigger in volume.
• With the mixer on low speed, add ⅓ of the flour mixture, followed by ½ of the buttermilk, another ⅓ of the flour, the second half of the buttermilk, and then the remaining flour mixture. Stir until just combined.
• Scrape down the sides and bottom of the bowl and mix again for another 20 to 30 seconds on low.
• Pour about 10 ounces of batter in a separate mixing bowl. Gently fold the chocolate mixture into the new bowl of cake batter.
• Alternately add the vanilla and chocolate cake batters to the prepared pan. I like to use a small measuring cup to scoop the cake batter into the pan so I can easily layer the different flavors. Use a toothpick or knife to swirl the batter, but don’t mix it too much – you want the flavors to be distinct and separate.
• Bake for 45 to 50 minutes or until a toothpick inserted into the center comes out with a few moist crumbs on it.
• Remove from oven and let cool in the pan for about 15 minutes before inverting onto a wire cooling rack to cool completely.

FOR THE BUTTERCREAM

• In the bowl of a stand mixer fitted with the paddle attachment, beat the butter and peanut butter until smooth, about 2 to 3 minutes.
• With the mixer on low, gradually add the powdered sugar, followed by the heavy cream, vanilla, and pinch of salt.
• Turn the mixer to medium-high and beat for an additional 2 to 3 minutes.

Course: Dessert

Cuisine: Cake

Keyword: Marble Cake, Marble Loaf Cake, Peanut Butter Buttercream