STEP ONEHEAT oven to 350ºF. Spray two 9 x 1 1/2-inch round cake pans or a 13 x 9 x 2-inch baking pan with flour no-stick cooking spray.
STEP TWOCOMBINE cake flour, sugar, baking powder and salt in large bowl.
STEP THREEADD milk and shortening. Beat with electric mixer at medium speed 2 minutes, or beat vigorously by hand 300 strokes.
STEP FOURADD egg whites, milk and vanilla. Beat 2 minutes more or 300 strokes.
STEP FIVEPOUR batter into prepared pan(s). For the 9-inch round cake pans: Bake for 25 to 30 minutes or until a toothpick inserted in center comes out clean. For the 13 x 9 x 2-inch pan: Bake 35 to 40 minutes or until a toothpick inserted in center comes out clean.
STEP SIXCOOL 15 minutes; remove cake from pan(s) to cooling rack to cool completely. Frost as desired.