Combine ingredients for topping (all except for the apple slices) and set aside.
Slice apples 1/4 inch thick.
Combine flour, sugar and baking powder together. Cut butter into mixture.
Beat egg with sour cream and vanilla and pour, all at once, over dry ingredients.
Stir quickly with a fork until just blended (batter will be lumpy).
Quickly spread into an 8 inch square baking pan.
Arrange fruit slices in rows over the batter.
Spoon brown sugar topping over fruit.
Bake at 400 degrees for 30-35 minutes. Enjoy!