Preheat Oven and Prepare Pan:
Preheat your oven to 350°F (175°C).
Grease and flour a 9-inch round cake pan or springform pan.
Mix Dry Ingredients:
In a medium bowl, whisk together flour, baking powder, baking soda, salt, and ground cinnamon. Set aside.
Cream Butter and Sugars:
In a large mixing bowl, beat the softened butter, granulated sugar, and brown sugar together until light and fluffy.
Add Eggs and Vanilla:
Beat in eggs one at a time, then stir in vanilla extract.
Combine with Dry Ingredients:
Add the dry ingredients to the butter mixture in thirds, alternating with sour cream, starting and ending with the dry ingredients. Mix until just combined.
Fold in Apples:
Fold in the chopped apples.
Pour into Pan and Add Topping:
Pour the batter into the prepared cake pan.
If using, arrange thinly sliced apple rounds on top and sprinkle with a little cinnamon sugar.
Bake:
Bake in the preheated oven for about 45-50 minutes, or until a toothpick inserted into the center of the cake comes out clean.
Cool and Serve:
Let the cake cool in the pan for about 10 minutes, then transfer it to a wire rack to cool completely.
Serve as is or with a dollop of whipped cream or ice cream.
Enjoy your delightful homemade cinnamon apple cake, perfect for a cozy dessert or a special treat!