Preparation

Preheat oven to 350°F. Prepare baking pan(s). Lightly butter or spray two 8 or 9 - inch round cake pans with cooking spray; cut rounds of parchment to fit the bottoms of the pans and place in pans, butter or spray again. Or line 24 standard muffin cups with cupcake liners, or lightly coat a 13 x 9 x 2 - inch pan with cooking spray. Place flour, baking powder, and salt in a medium bowl. Mix using Speed 1 for 15 seconds to combine and aerate. Reserve. Place butter and sugar in a large mixing bowl. Mix on Speed 1 for 40 seconds, then cream on Speed 3 for 2 - ½ minutes, until light and fluffy. Add eggs one at a time, mixing on Speed 2 for 20 seconds after adding each egg. Add flour mixture, milk, and vanilla on Speed 1, mix until blended and smooth, 1 minute. Divide batter evenly among prepared pans. Bake in preheated oven until a cake tester comes out clean when inserted in the center of the pan: 30 - 32 minutes for 8 - inch layers; 25 - 28 minutes for 9 - inch layers; 30 - 35 minutes for a 13 x 9 - inch cake. Cool in pan for 10 minutes, loosen sided of cake from pans with a thin knife, then remove from pan and place on a wire rack; remove parchment. Cool completely before frosting. To assemble layer cakes: Place one cake layer on plate. Spread ⅓ of frosting over cake. Top with second layer; spread remaining frosting over top and sides of cake. Allow cake to stand 2 hours before serving. (Can be prepared 1 day ahead. Cover and refrigerate. Bring to room temperature before serving.)