Sift first 3 ingredients together 3 times into a medium bowl; set aside.
Beat egg whites, cream of tartar, and salt in a large bowl at high speed of an electric mixer until foamy. Gradually add 1/4 cup sugar, beating until soft peaks form. Sift flour mixture over egg white mixture, 2 tablespoons at a time; fold in gently after each addition. Fold in flavorings.
Spoon batter evenly into 4 (4-inch) tube pans coated with cooking spray, spreading evenly. Break large air pockets by cutting through batter with a knife.
Bake at 350° for 30 minutes or until cake springs back when lightly touched. Remove cakes from oven; invert pans, and cool completely. Carefully loosen cakes from sides of pans, using a narrow metal knife; remove from pans. Sift powdered sugar over cooled cakes.