Cream sugar and butter thoroughly. Add vanilla.
Sift together flour, baking powder and salt. Add dry ingredients and water alternately to mixture.
Beat egg whites until soft peaks form. Gradually add baking powder to egg whites. Beat until stiff peaks form. Fold beaten egg whites into batter. Pour into prepared cake pan.
Bake for 45 minutes or until a cake tester comes out clean. Top cooled cake with frosting of your choice.