Position racks in top and bottom thirds of oven and preheat to 350° F
Butter one 12-inch-diameter cake pan* with 3-inch-high sides, one 9-inch-diameter cake pan with 3-inch-high sides and one 6-inch-diameter cake pan with 3-inch-high sides
Line bottoms with parchment. Sift flour, baking powder and salt into medium bowl
Using handheld electric mixer, beat butter in 12-quart bowl on medium-high speed until light
Gradually add sugar and beat until well blended. Beat in extracts. On medium-low speed, beat in dry ingredients alternately with milk in 3 additions each, beating just until combined (batter will be thick)
Using electric mixer fitted with clean, dry beaters, beat whites in another large bowl until stiff but not dry
Fold 1/3 of whites into batter to lighten. Fold in remaining whites. Spoon batter into prepared pans so that depth of batter is the same in each pan; smooth tops
Bake until tops are deep golden brown and tester inserted into center comes out clean, about 55 minutes for 6-inch cake, about 1 hour 5 minutes for 9-inch cake and about 1 hour 20 minutes for 12-inch cake
Cool cakes in pans on racks 20 minutes. Run knife around pan sides to loosen cakes. Turn out cakes onto racks and peel off parchment. Cool cakes completely.
