Preheat oven to 375 °F. Sift flour, baking powder and ¾ cup Sugar. Beat egg whites until soft peaks form. Add remaining Sugar and beat until stiff peaks form. Make a well in dry ingredients. Add oil, ½ cup milk and flavoring. Beat 150 strokes (or 1 minutes. at medium speed. ) Add remaining milk. Beat again 150 strokes. Mix 1/3 of egg mixture with batter. Then fold batter into remaining egg whites. Turn into 2 lightly oiled (or greased with margarine) 8-inch layer pans. Bake about 30 minutes. Cool 10 minutes and remove from pans. Note: Instead of using vanilla you may substitute 2 teaspoons of grated lemon rind.