Sift flour with 3/4 cup sugar four times. Beat egg whites, cream of tartar, salt and vanilla until stiff enough to hold up in soft peaks, but still moist and glossy. Add remaining 3/4 cup sugar to whites, 2 tablespoons at a time, beating after each addition. Sift about 1/4 of flour over whites, fold in. Fold in remaining flour by fourths. Bake in an ungreased 10″ round tube pan in moderate oven. Bake at 375 degrees for 35-40 minutes. Invert pan, cool.