Use a N-50 mixer, wire whip. Whip at third speed until the specific gravity of the whites falls into the range of 0.11-0.12 (approximately 120 s on third speed). Sift flour and powdered sugar together. Add along with vanilla to the whites. Mix 15 s on first speed. Remove from mixer and fold in flour 3 times by hand with a rubber spatula. The specific gravity should fall into a range of 0.22-0.28. Scale 560 g batter into a tube pan 9.25 in. T.I.D. (3.125 in. cone)x3.5 in. deep. Bake 37-38 min at 375 F. Cool (upside down) for 1 h.