Preheat oven to 375 degrees F. Spray a pie pan with non-stick cooking spray. (If using a darker pan, decrease temp to 350°F)
Cream together butter, shortening, sugar, egg and the vanilla.
Blend in the flour, cream of tartar, soda and salt.
Take about 2/3 of the snickerdoodle dough and press it flat into the bottom of the pie pan, pressing against the edges so that they rise just a bit around the sides of the pan.
Sprinkle half the cinnamon sugar mixture on top of the dough.
Spread apple pie filling over the dough, making sure it extends to all sides.
Take the remaining cookie dough and crumble it with your fingers, placing small pieces covering the top of the apple pie filling. It won't completely cover it, but it will be close.
Sprinkle the remaining cinnamon-sugar mixture on top.
Cover pie with foil. (I sprayed the side that would be touching the dough with non-stick spray.)
Bake at 375 degrees F for 20-25 minutes on the middle rack of the oven. Remove foil and bake another 5 minutes.
Let cool for 10 minutes and serve, topped with ice cream caramel sauce if desired.