1/2 cup butter, softened
1 1/2 cups flour
1/4 tsp salt
1 tsp cream of tartar
1 1/2 tsp cinnamon
3/4 cup sugar
Preheat oven to 350 degrees. Spray a 9" glass pie plate well with cooking spray, including up the sides. Set aside; also grease one cookie sheet- you'll see why.
In mixing bowl, cream butter until light; add egg and beat well. Add the dry ingredients and blend until a dough forms.
Now here's the funny part- (for me anyway) take out enough dough to make four or five cookies- 1" balls each. Roll in a mixture of cinnamon and sugar- about 1/4 cup sugar mixed with 1/2 tablespoon cinnamon. Arrange two inches apart on greased baking sheet and bake for about 15 minutes. Cool, then eat while you make the rest of the pie! (sorry, I had too much dough for the pie plate and needed to reduce it by just a little- and didn't want to waste any!!)
Now, with the rest of the dough, pat into the greased pie plate, on the bottom and up the
rim. Prick all over with a fork. Bake at 350 degrees for about 20 minutes, until dry but not
really browned. Cool.
Pour filling into cooled Snickerdoodle crust. Sprinkle the whole top with the cinnamon-sugar mixture. Bake 30-40 minutes, or until a knife inserted in center comes out clean. Check after 30 minutes- you don't want it over-baked. Lay a piece of foil over the top if the crust edge is browning too much before the filling is done.