Preheat oven to 350°F. Spray two 9 in. round pans with vegetable cooking spray.
In medium bowl, sift together flour and baking powder; set aside. In large bowl, beat butter and sugar with electric mixer until light and fluffy; add vanilla and beat well. Add flour mixture to butter mixture alternately with milk; beat well after each addition. In separate bowl, beat egg whites until stiff but not dry; gently fold into batter. Divide evenly into prepared pans.
Bake 33-38 minutes or until toothpick inserted in center of cake comes out clean. Cool 10 minutes in pan on rack; remove and cool completely before decorating.