Sift together dry ingredients. In small mixer bowl, combine egg yolks, grapefruit juice, water and oil. Add dry ingredients. Beat at low speed until blended. Then beat at medium speed for one min. *Stir* in grapefruit peel. Beat whites until frothy; add cream of tartar. Continue beating until whites are stiff, But Not Dry.

Carefully folk yolk mixture into whites until just blended. Pour into 9-inch layer cake pans lined with oiled waxed paper. Bake at 350 F for 25-30 minutes. Leave in pans 10 minutes. Turn out onto wire rack to cool. Frost.