1 hour 45 minutes
Yellow cake mix is widely available in grocery stores if you’re short on time and need a cake in a jiffy, but it’s worth taking the time to make one from scratch. The vast majority of homemade cakes employ a technique called creaming, in which fat (usually butter) is beaten with sugar until light and fluffy. This remarkable yellow cake recipe uses a process called reverse creaming instead. You’ll start by combining the dry ingredients, then adding the room-temperature butter, and mixing until just sandy. The wet ingredients go in together and are then mixed until just incorporated. This method helps to better aerate the batter and prevents gluten from overdeveloping, leaving you with a light, tender cake that stays moist. Finish it all off with a richly flavored chocolate frosting.
Makes two 9"-diameter cakes
Place a rack in middle of oven; preheat to 350°. Butter two 9"-diameter cake pans and line each bottom with a parchment paper round; butter parchment. Using an electric mixer on low speed, mix 3 cups (345 g) cake flour, ¾ cup (150 g) granulated sugar, 1 Tbsp. baking powder, 1 tsp. baking soda, and 1 tsp. Diamond Crystal or ½ tsp. Morton kosher salt in a large bowl until combined, about 30 seconds.
With the motor running, add ¾ cup (1½ sticks) unsalted butter, room temperature, cut into pieces, then increase speed to medium and beat until butter is in small pieces and mixture looks sandy, about 3 minutes.
Turn off mixer and add 4 large eggs, room temperature, 2 large egg yolks, room temperature, 1½ cups buttermilk, room temperature, and 1 Tbsp. vanilla extract. Beat on medium-high speed until pale yellow and fluffy, about 1 minute (be careful not to overmix batter). Divide batter between prepared pans and smooth tops with an offset spatula.
Bake cakes until tops are golden and spring back when gently pressed, 30–35 minutes. Transfer pans to a wire rack and let cakes cool in pans 15 minutes. Run a small knife or offset spatula around inside of pans to loosen cakes, then turn out onto rack. Remove parchment and let cakes cool completely, about 1 hour.
Frosting and assembly
While the cakes are cooling, sift 4 cups (440 g) powdered sugar and 1½ cups (126 g) unsweetened Dutch-process cocoa powder into a medium bowl. Using an electric mixer with clean beaters (or paddle) on medium speed, beat 1½ cups (3 sticks) unsalted butter, room temperature, and ¾ tsp. Diamond Crystal or ½ tsp. Morton kosher salt in a large bowl until creamy, about 4 minutes. Add half of dry ingredients and beat on low speed until incorporated. Add remaining dry ingredients and ¼ cup plus 2 Tbsp. buttermilk, room temperature, and beat until thoroughly combined. If frosting is too stiff, thin with more buttermilk (1–2 Tbsp.) until it reaches a spreadable consistency.
Using a large serrated knife, slice domed tops from cakes. Place 1 layer on a large plate or cake stand and spread a thick layer of frosting on top with an offset spatula. Place second cake layer on top and generously frost top and sides of cake with remaining buttercream. Smooth sides and create decorative swoops and swirls on the top.