Preheat oven to 400 degrees F. In a large skillet melt margarine or butter. Add the apple slices, brown sugar, and cinnamon. Cook, covered, over medium heat about 6 minutes or until the apples are just tender, stirring occasionally. Gently stir in the 1/2 cup raspberries. Set aside.
In a small mixing bowl stir together the flour, baking powder, and salt; set aside. In a medium mixing bowl beat the egg whites with an electric mixer on medium to high speed until soft peaks form (tips curl). Gradually beat in granulated sugar, 1 tablespoon at time, until stiff peaks form (tips stand straight). In a large mixing bowl beat the egg yolks until combined. Alternately stir flour mixture and milk into beaten egg yolks. Gently fold in the egg whites, leaving a few fluffs of egg white in the batter.
Preheat a greased 10-inch, ovenproof skillet by placing it in the hot oven for 10 minutes. Pour half the batter into the preheated skillet. Spoon the cooked fruit over the first layer of batter; carefully pour remaining batter over fruit.
Bake for 20 to 25 minutes or until a knife inserted near the center comes out clean. Sprinkle with powdered sugar and, if desired, fresh raspberries or other fruit. Cut into 6 wedges to serve. If desired, serve with maple- or fruit-flavored syrup. Makes 6 servings.