In a medium bowl stir together flour, baking powder and baking soda.
In a large bowl with an electric mixer cream butter and sugar on low speed. Stir in eggs one at a time. Add in vanilla. Gradually add in flour mixture, alternating with some of the sour cream until all blended.
Pour into prepared cake pan. Stick apples lightly into top of dough. Sprinkle with crumb topping.
Bake in preheated oven for 45 to 50 minutes until it pulls away from the side of the pan.
Cool on rack.