Apple Caramel Cake

ngredients:
Batter:
2 c unbleached flour
1 3/4 c brown sugar -- packed
4 tsps cinnamon
1 tsp baking powder
1/2 tsp baking soda
1/4 tsp salt
3/4 c reduced fat margarine -- softened
2 tsps pure vanilla extract

6 whole egg whites -- slightly beaten
2 c apples -- peeled and sliced
Topping:
1 1/2 c powdered sugar -- sifted
1/4 c reduced fat margarine -- melted
1/4 c brown sugar -- packed
1 tsp pure vanilla extract
4 tsps skim milk

Directions:

Preheat oven at 350. Prepare a 12-cup fluted pan with cooking spray and flour; set aside. To prepare batter, combine flour, 1 3/4 cup brown sugar, cinnamon, baking powder, and baking soda in a mixing bowl. In another mixing bowl, combine 3/4 cup margarine, 2 teaspoons vanilla extract, egg whites, and apples. Mix dry ingredients with wet ingredients just until moistened. Pour batter into prepared pan. Bake for 45 minutes. Cool upright for 30 minutes; invert onto serving plate. Meanwhile, to prepare topping, combine powdered sugar, remaining margarine, brown sugar, remaining vanilla extract, and milk. Immediately spoon over cooled cake.