Preheat oven to 350°
Peel, core, and slice apples into sixteenths.
Spray 8 inch cake or tart pan with non-stick spray.
In the bowl of an electric mixer, cream the butter and sugar until it becomes light and fluffy. Add the egg and mix until thoroughly combined.
Add flour and baking powder and mix until just combined.
With floured fingers, press dough into the prepared pan, pushing the dough slightly up the edges.
Arrange the apples in concentric circles and press into the dough. Sprinkle with the cinnamon sugar topping.
Bake for about 45 minutes or until nicely browned. Let cool completely.
Optional: drizzle with an icing glaze made up of confectioner's sugar and water.