Grease well a 10-inch ovenproof skillet with flared sides or a 2-quart rectangular baking dish; set aside.
Combine flour, baking powder, and salt; set aside. Beat egg whites in a medium bowl with an electric mixer on medium to high speed until soft peaks form (tips curl). Gradually beat in 1/4 cup of the sugar, 1 tablespoon at a time, beating until stiff peaks form (tips stand straight).
Pour egg product into a large mixing bowl. Alternately add flour mixture and milk, whisking until mixed after each addition. Stir in chopped apple, shredded cheese, and lemon juice. Gently fold in beaten egg whites, leaving a few puffs of egg white. Do not overmix. Pour batter into prepared skillet or baking dish; spread to edges. Combine remaining 4 teaspoons sugar and the cinnamon; spinkle over batter.
Bake in a 400 degree F oven for 20 to 25 minutes or until a knife inserted near center comes out clean. To serve, cut into wedges or squares. Garnish with sour cream and apple slices, if desired. Makes 8 servings.