Preheat oven to 350*.Spray a 13 x 9 inches pan with non-fat vegetable cooking spray.
Combine flour and baking powder; set aside. Cream butter and sugar in large bowl with electric mixer on medium speed until light and fluffy. Add eggs, one at a time, beating well after each addition. Mix in vanilla. Gradually add flour mixture, beating until well blended after each addition. Pour into prepared baking pan.
Bake until toothpick inserted in center comes out clean. About 30 minutes.Pierce warm cake with large fork at 1/2-inch intervals. Combine the three milk products. Pour slowly over top of cake. (Milk mixture will slowly be absorbed by the cake.) Cool completely. Cover.
REFRIGERATE 1 hour or until ready to serve. Frost cake with the whipped topping just before serving. Store leftover cake in the refrigerator.