Preheat oven to 375.
In a large bowl, combine flour, sugar, baking powder, baking soda, cinnamon, and salt.
In a medium bowl, combine eggs, oil, vanilla and milk.
Pour the wet ingredients into the dry ingredient bowl and mix to combine.
Pour half of the batter into a greased 8x8 or 9x9 pan.
Spread apple pie filling over the batter.
Pour the remainder of the batter on the top of the apples, covering completely.
For the crumb topping, mix in butter with flour, cinnamon and brown sugar until crumbs form. Sprinkle crumbs over top of cake.
Bake at 375 for 40 minutes or until a toothpick inserted in the center comes out clean. If the topping begins to brown to much cover with foil for the remainder of the cooking time. Oven cook times vary so check your cake every so often.