• Preheat the oven to 350F. Generously butter your cast iron skillet.
• Cream the butter and sugar together until light and fluffy. Beat in the egg, scraping down the sides of the bowl to get everything well incorporated.
• Beat in the sour cream, vanilla, and apple pie spice until smooth and creamy.
• At this point I core and slice the apple into thin slices. Toss with a little lemon juice if you are worried about it browning. Set aside. Note: whether to peel or not is up to you. I like the little bit of red color from the peel so I leave it on.
• In a separate bowl, whisk together the dry ingredients to get everything well blended and lump free. Fold the dry ingredients into the batter and mix just until the dry ingredients are well incorporated, but don't over mix at this point.
• Turn the batter into your prepared pan and spread out evenly.
• Arrange the apple slices over the top of the batter in any pattern you like. Sprinkle evenly with the tablespoon of granulated sugar.
• Bake for 40-45 minutes until golden, the very center looks cooked, and a toothpick inserted in the center comes out without wet batter on it. Note: the toothpick may look moist, that's ok. Try not to over bake this cake.
• Let cool briefly on a rack before slicing and serving.

to make the whipped sour cream

• Whip the heavy cream, sour cream, and powdered sugar using electric beaters until the mixture thickens and creates soft peaks. Once the mixture starts to thicken slow your beaters so you don't risk over beating it.