Grease and lightly flour two 9-inch round cake pans. Combine flour, baking powder and salt. In a mixer bowl, beat shortening using medium speed for about 30 seconds. Add sugar and vanilla and beat until fluffy. Add dry ingredients and milk alternately to beaten mixture, beating on low speed after each addition. Wash beaters. In a small mixer bowl, beat egg whites until stiff peaks form. Gently fold into batter. Turn into pans. Bake at 375 about 20 minutes or until cake tests done. Cool 10 minutes in pans. Remove from pans and cool on wire racks.