This is a recipe that I got from the Simply Recipes Blog. I made it today and it is really good.
Serves 6
1 cup flour
1 teaspoon baking powder
1/2 teaspoon salt
2/3 cup sugar
1 teaspoon ground cinnamon
5 1/2 tablespoons unsalted butter, at room temperature
1 egg beaten
1/2 cup milk
1 medium baking apple, peeled and sliced

Preheat oven to 375 degrees. Grease a 9 inch square or round baking dish with a 4 cup capacity.

Sift together the flour, baking powder and salt. In a separate bowl combine 1/3 cup sugar with the cinnamon and set aside.

In the bowl of an electric mixer, cream the butter with the remaining 1/3 cup sugar. Beat in the egg until well blended. Add the flour mixture in three additions, alternating with the milk, beating until just combined.

Spread half the mixture in a baking dish. Lay the apple slices on the batter so they just cover the batter. Overlap them if necessary. Sprinkle the apples with half of the cinnamon-sugar mixture. Spread the rest of the batter over the apples. Sprinkle the remaining cinnamon-sugar on the top.

Bake the cake for 25 minutes or until golden brown and apples start to bubble at the edges.