Preheat oven to 325 degrees F. Spray bottom and sides of an 8 or 9 inch square pan with cooking spray.
CARAMEL TOPPING
In a small saucepan, melt the butter over medium heat, stirring occasionally. Stir in the brown sugar. Heat to boiling; remove from heat. Stir in ½ teaspoon cinnamon.
Pour into the pan; spread evenly over the bottom of the pan. Arrange apple wedges over the brown sugar mixture, overlapping and layered as needed.
CAKE
In a medium bowl, whisk together the flour, baking powder, cinnamon and salt. Set aside.
In a large bowl, use an electric mixer to beat the sugar and butter, beating until fluffy (scrape down sides as needed). Beat in the eggs until smooth. Add the vanilla. Gradually beat in the flour mixture alternately with the milk, beating after each addition until smooth. Spread the batter evenly over the apples.
In a large bowl, use an electric mixer to beat the sugar and butter, beating until fluffy (scrape down sides as needed). Beat in the eggs until smooth. Add the vanilla. Gradually beat in the flour mixture alternately with the milk, beating after each addition until smooth. Spread the batter evenly over the apples.Bake 50 to 55 minutes, or until a toothpick inserted into the center comes out clean. Cool for 15 minutes, then run a knife along the edges of the pan to loosen the cake. Place a serving plate upside down over the pan; turn plate and pan over, and remove the pan.
TOPPING
Beat whipping cream with a heaping tablespoon of powdered sugar until it reaches whipped cream consistency.
Serve cake warm topped with whipped cream.
Notes
High Altitude changes (3500 to 6500 feet): Change oven temperature to 350 degrees. Increase flour to 1½ cups. Decrease sugar in cake to ¾ cup.