Instructions

• Preheat oven to 350°F (175°C). Grease the sides of three 8-inch cake pans, line the bottoms with parchment circles sized to fit, and grease the parchment.
• In a medium bowl whisk together 2 1/4 cups all-purpose flour, 2 teaspoons baking powder, 1/2 teaspoon baking soda, and 1/4 teaspoon salt. Set aside.
• In a smaller bowl whisk together 2 tablespoons cocoa powder, 1 tablespoon vinegar, 2 teaspoons vanilla extract, and 1 tablespoon red gel food coloring until smooth and evenly colored.
• In the bowl of a stand mixer (or a large bowl with a hand mixer) cream 1/2 cup softened butter and 1 1/2 cups sugar on medium speed until light and fluffy, about 2–3 minutes. Scrape down the bowl as needed.
• Add the cocoa-color mixture to the creamed butter and sugar and beat until incorporated. Add the 2 eggs, one at a time, beating until each is fully incorporated and the batter is smooth.
• With the mixer on low, add half of the dry flour mixture and mix until just incorporated. Add half of the 1 cup buttermilk and mix until smooth. Repeat with the remaining flour mixture and the remaining buttermilk, mixing until the batter is smooth and uniform.
• Divide the batter evenly among the three prepared pans and smooth the tops. Bake 30–35 minutes, or until a toothpick inserted into the center comes out clean. Cool in the pans for 5 minutes, then run a knife around the edges, invert the cakes, and transfer to a wire rack to cool completely.
• Using a serrated knife, level and remove the domes from each cooled cake. Break the trimmed pieces into crumbs and spread them in an even layer on a baking sheet.
• Bake the crumbs on the baking sheet for 15 minutes to dry them. Let the crumbs cool completely.
• Place the cooled crumbs in a food processor and pulse until very fine (about 30 seconds–1 minute). Set the fine crumbs aside.
• For the frosting base (stabilized roux): from the 3/4 cup unsalted butter measured for the frosting, measure out and melt 2 tablespoons in a small saucepan over medium heat. Whisk in 2 1/2 tablespoons all-purpose flour and cook, whisking constantly, for 1 minute.
• Gradually whisk in 1/2 cup milk, 1/2 teaspoon vanilla extract, and 1/4 teaspoon salt. Whisk constantly until the mixture thickens into a paste (about 1 minute). Transfer the paste to a small bowl, press plastic wrap directly onto the surface to prevent a skin, and cool completely (refrigerate to speed cooling if desired).
• Transfer the cooled paste to a larger mixing bowl. Add the remaining butter from the 3/4 cup (the rest of the measured 3/4 cup), 8 ounces softened cream cheese, and beat until smooth and well combined. Add 1 cup icing sugar and beat until the frosting is smooth and creamy. If the frosting is too soft, chill briefly and rebeat.
• To assemble the cake, place four 6x6-inch parchment squares overlapped on your cake platter to protect the platter. Set one cake layer in the center (right-side-up) and spread about 3/4 cup of frosting evenly over the top.
• Place the second cake layer on top and spread another 3/4 cup of frosting evenly over that layer.
• Place the final cake layer on top with its top-side-up. Use the remaining frosting to cover the top and sides of the cake evenly.
• Sprinkle about 1/2 cup of the fine cake crumbs over the top and gently press them into the frosting. Press additional crumbs onto the sides with your hands or a spatula until the cake is evenly coated.
• Carefully pull out the parchment squares from under the cake, wipe any stray crumbs from the platter, slice, and serve.