White Cake: Cream shortening; add sugar gradually and cream thoroughly.
Sift flour, baking powder and salt together and add to sugar mixture alternately
with the milk and water mixed. Add vanilla extract and fold in egg whites. Pour
into 2 well-greased and floured 8-inch cake pans.
Bake at 350 degrees F for 30 to 35 minutes.
Cool. Remove from pans.
Lemon Filling: Beat egg yolks and add remaining ingredients. Place mixture
in top of double boiler and cook over hot water until thick.
Let filling cool, then spread between cake layers.