In small bowl, sift together flour, baking powder and salt. In large
bowl, whip egg whites with electric mixer until foamy. Add cream
of tartar and whip until stiff but not dry. In clean bowl, whip egg
yolks 1 minute; add vanilla and gradually add sugar, whipping
until mixture is pale yellow and doubled in volume. With rubber
spatula, fold 1/3 of egg whites into yolks to loosen; fold in
remaining whites until nearly combined. Add flour and fold
until no streaks remain. Fill cavities about 3/4 full with batter;
smooth the tops.