Whisk together all the dry ingredients.
Whip together the butter, sour cream and eggs.
Stir all together with spatula, just until mixed. Don't overmix.
Mix streusel and set aside.
Spread half the batter into a 13" x 9" baking pan.
Spread the pie filling over the layer of batter.
Sprinkle with half the streusel.
Dollop the remaining cake batter on top of the layers in the pan.
Sprinkle with the rest of the streusel.
Bake at 350° for 25 to 30 minutes.