Red Velvet Cake

Make the cake: Heat oven to 350°. Butter and flour two 8″ cake pans, and set aside. Whisk together flour, cocoa, baking powder, and salt in a bowl; set aside. Whisk together buttermilk, food coloring, vinegar, and vanilla in a bowl; set aside. In the bowl of a stand mixer fitted with a paddle, cream butter and sugar on medium-high speed until pale and fluffy, about 3 minutes. Add eggs, one at a time, beating well after each addition. On low speed, alternately add dry ingredients in 3 batches and wet ingredients in 2 batches. Increase speed to high and beat until batter is smooth, about 5 seconds. Divide batter between prepared pans, and smooth top with a rubber spatula; drop pans lightly on a counter to expel any large air bubbles. Bake cakes until a toothpick inserted in middle comes out clean, about 30 minutes. Let cakes cool for 20 minutes in pans; invert onto wire racks, and let cool.

Make the frosting and assemble cake: Whisk together sugar and flour in a 4-qt. saucepan; add milk and whisk until smooth. Stirring often, bring to a boil over medium-high heat; cook, stirring constantly, until very thick, about 5 minutes. Remove pudding from heat; cool. In the bowl of a stand mixer fitted with a paddle, beat butter and 1⁄4 of the pudding on medium-high speed until fluffy and smooth, about 1 minute. Add half the remaining pudding, beating until smooth, and then add remaining pudding and vanilla. Increase speed to high and beat frosting until white and fluffy, about 3 minutes. To assemble, place one cake on a cake stand, and spread with 1 1⁄2 cups frosting. Place second cake over frosting; cover top and sides with remaining frosting; chill to firm frosting. Serve at room temperature.