Preheat oven to 350-degrees F. Grease a cake pan with butter or margarine, or nonstick cooking spray. Line pan with sprayed waxed paper. Sift flour and powdered sugar into a small bowl and set aside.
In large bowl, with mixer at high speed, beat egg whites until soft peaks form. Beat in 2/3 cups sugar, 2 tablespoons at a time, to the whites, beating just until whites stand in stiff, glossy peaks.
Sift flour mixture, one-third at a time, over beaten egg whites; fold in with rubber spatula just until flour mixture is unseen.
Spread batter into prepared pan evenly. Bake 25-30 minutes, or until cake springs back when touched. Cool completely in pan on wire rack. Invert cake onto cutting board; carefully peel off waxed paper and continue cooling until ready to eat.