Preheat your oven to 325 degrees F. Spray the bottom and sides of an 8 or 9-inch square pan with cooking spray.
In a small saucepan, melt the butter over medium heat, stirring occasionally. Stir in the brown sugar and heat until boiling. Remove from heat and stir in ½ teaspoon ground cinnamon.
Pour the caramel mixture into the pan, spreading it evenly. Arrange the apple wedges over the caramel, overlapping as needed.
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 granulated sugar and ½ cup butter until fluffy. Beat in the eggs one at a time, then add the vanilla extract.
Gradually beat in the flour mixture alternately with the milk, until smooth. Spread the batter over the apples.
Bake for 50 to 55 minutes, until a toothpick inserted in the center comes out clean.
Let cool for 15 minutes. Run a knife around the edges to loosen the cake. Invert onto a serving plate.
Beat the heavy whipping cream with powdered sugar until whipped. Serve the cake warm topped with whipped cream.
