Baking this cake in a 13x9-inch pan instead of in the traditional round layer pans makes it easier to bring this frosted cake to a potluck or other gathering.
If you don't have buttermilk, just add 1 Tbsp. lemon juice or vinegar to 1 cup milk; let stand 10 min. or until thickened before using as directed.
How to Store the Leftover frosting
Spoon leftover frosting into freezer container. Freeze up to 3 months. Thaw overnight in refrigerator before using as desired.