Preheat oven to 350 degrees F. Lightly spray a 9-inch springform pan.
In a medium bowl, whisk together the flour, baking powder, salt, and cinnamon. Set aside.
Using the paddle attachment on a stand mixer, cream the butter, brown sugar, and sugar for several minutes, stopping once to scrape down sides of bowl.
Add eggs, one at a time, and beat for around one minute after each addition. Add vanilla and mix well.
Alternating, add half of the dry mixture, then the sour cream, and finish with the remaining half of the dry mixture. Mix until just combined.
Gently fold in the diced apples and pour into prepared pan. Use an offset spatula or back of spoon to even out the batter. Arrange remaining apple slices on top of batter in preferred pattern.
Bake for 40-45 minutes, or until the cake is no longer wiggly in the center.
Let cake cool for 10-15 minutes on wire rack. Run a knife along the rim of cake and unlatch to remove outer ring. Cool completely before slicing.