For the cake:
- 3 cups all-purpose flour
- 1 3/4 tsp. baking powder
- 1 1/4 tsp. salt
- 16 Tbs. (2 sticks) unsalted butter
- 2 cups granulated sugar
- 4 eggs, lightly beaten
- 1 tsp. vanilla extract
- 1 1/3 cups milk
For the buttercream:
- 4 Tbs. (1/2 stick) unsalted butter
- 1 1/2 cups confectioners' sugar, sifted
- 1 Tbs. milk
- 1/2 tsp. vanilla extract
- Pinch of salt
Position a rack in the lower third of an oven and preheat to 325°F. Grease and flour a championship cake pan. To ensure easy release and excellent definition of the pattern, flour the pan with Wondra® flour, a fine flour typically used to thicken gravy. Tap out excess flour.
To make the cake, over a sheet of waxed paper, sift together the flour, baking powder and salt; set aside.
In the bowl of an electric mixer fitted with the flat beater, beat the butter on medium speed until creamy and smooth, about 30 seconds. Add the granulated sugar and continue beating until light and fluffy, about 5 minutes, stopping the mixer occasionally to scrape down the sides of the bowl. Add the eggs a little at a time, beating well after each addition. Beat in the vanilla just until incorporated, about 1 minute.
Reduce the speed to low and add the flour mixture in three additions, alternating with the milk and beginning and ending with the flour. Beat each addition just until incorporated, stopping the mixer occasionally to scrape down the sides of the bowl.
Spoon the batter into the prepared pan, spreading the batter so the sides are higher than the center. Bake until the cake begins to pull away from the sides of the pan and a toothpick inserted into the center comes out clean, 45 to 55 minutes. Transfer the pan to a wire rack and let the cake cool upright in the pan for 15 minutes.
Meanwhile, make the buttercream: In a small bowl, using a handheld mixer, beat the butter on medium speed until smooth and creamy, about 1 minute. Add the confectioners' sugar, milk, vanilla and salt and continue beating until light and fluffy, 2 to 3 minutes more.
Tap the cake pan gently on a work surface to loosen the cake. Set the rack over the cake, invert the pan onto the rack and lift off the pan. Let the cake cool completely, at least 2 hours, before assembling.
Return both halves of the cooled cake to the pan. (This is easily done by placing the pan over the cake halves and inverting the rack onto the pan.) Level the cake by using a serrated knife to gently saw off the part of each cake half that rose above the edge of the pan. Then remove one half of the cake from the pan.
Spread a thin layer of buttercream, about 2/3 cup, over the cut side of the cake half that is still in the pan. Place the other half on top of the buttercream and press down gently to secure the two halves. Cover loosely with plastic wrap and refrigerate the cake until the buttercream is firm, about 30 minutes.
In the center of a serving plate, place a mound of buttercream half the size of the cake's base. Remove the cake from the pan by lifting the pan vertically and tilting it forward, then catching the cake with your hand. Place the cake upright on the plate, on top of the buttercream. Decorate the cake as desired. Serves 16.