In small bowl, sift together flour, baking powder and salt; set aside. Separate eggs; beat whites until foamy. Add cream of tartar and beat until stiff but not dry. In clean bowl, beat egg yolks 1 minute; add vanilla extract and gradually add sugar, beating until pale yellow and doubled in volume. Add flour mixture, beating until just combined. Fold 1/3 of egg whites into yolk mixture to loosen; fold in remaining whites until no streaks remain. Pour batter into pan, spreading evenly from center out.