Sift flour and 1/2 c. sugar together 4 times. Beat whites until frothy. Beat in cream of tartar and vanilla. Beat until tips of peaks fold over slightly. Sprinkle remaining sugar over surface 2 tablespoons at a time and fold in. Sift 4 tablespoons flour over surface and fold in. Repeat until all flour is added. Slide gently into a 9-inch tubed pan - cut through batter with spatula to break large air bubbles. Bake at 375 degrees F. about 30 minutes. Invert and allow to cool in pan.