• Preheat oven to 350°F.
• In large mixing bowl beat the butter until creamy. Add the sugars and mix until light and fluffy.
• Add the eggs and mix until combined. Stir in the vanilla and sour cream.
• In a medium size mixing bowl combine the flour, baking powder, salt, and cinnamon, whisk together.
• Slowly add half of the flour mixture to the wet ingredients. Mix gently until just combined. Pour in the milk, mixing slowly. Add the remaining flour mixture and mix gently to combine.
• Fold in the chopped apple.
• Spray an 8 inch cast iron skillet with non stick baking spray, and pour in the batter.
• Bake for about 45 minutes or until top is golden and a toothpick inserted in the center comes out clean.

Caramel Topping

• Add the butter and milk to a small bowl, heat in microwave until the butter is melted.
• Stir in the powdered sugar, vanilla, and caramel until smooth (if you have bits of powdered sugar in the topping run through a fine mesh sieve if needed) Stir in the chopped apple.
• Once the cake is cooled carefully run a knife along the edge and turn over to remove the cake.
• Pour the caramel apple topping over the top of the cooled cake prior to serving.