Slice apples crosswise into 1/2-inch slices. Set aside 8 largest slices;reserve remaining apple for another use.
Lightly spoon flour into dry measuring cups, level with a knife. Combine flour, sugar, salt and nutmeg in a medium bowl. Stir in cider and egg whites (batter will be thick).
Heat a large nonstick skillet coated with cooking spray over medium-high heat. Dip 4 apple slices in batter, place in pan. Cook 2 minutes on each side or until lightly browned. Arrange apple slices on a baking sheet coated with cooking spray; lightly coat apples with cooking spray. Repeat with remaining apple slices.
Bake apples at 400°F for 10 minutes or until edges are crisp. Drizzle each of 4 plates with 1 tablespoon caramel sauce, top with 2 apple slices. Sprinkle with powdered sugar if desired. Serve immediately.