Heat oven to 425 degrees F.
Melt butter in large ovenproof skillet. Add apples, 2 tablespoons sugar; cook, stirring, 15 to 20 minutes, until apples are tender and liquid has evaporated. Stir in vanilla and cinnamon. Remove from heat.
Beat together milk, eggs, egg whites, remaining 1 tablespoon sugar and salt in bowl. Gradually whisk in flour until well blended and smooth. Pour batter over hot apples.
Bake in 425 degree F oven 20 minutes. Reduce heat to 350 degrees F; bake 10 to 15 minutes, until puffed and browned. Sprinkle with sugar. Cut into wedges. Makes 6 servings.