Grease (9 x 1 ½ inch) layer pans; line bottoms with waxed paper. Sift together dry ingredients into large bowl. Stir in Real Mayonnaise. Gradually stir in water and vanilla until smooth and blended. Pour into prepared pans. Bake in 350 degree F. (moderate) oven about 30 minutes or until cake test done. Cool. Remove from pans. Make 2 layers.