Preheat oven to 400°.
Mix together the flour, cream of tartar, and baking soda.
In the bowl of an electric mixer combine the butter, shortening, and sugar. Beat for 2 minutes.
Add the eggs one at a time beating well after each addition.
Spoon in the flour mixture, beating just until combined.
Gently roll the cookies into balls.
Mix together the cinnamon and sugar.
Roll balls in the cinnamon sugar and place on a cookie sheet covered in parchment paper or a silicone mat.
Bake at 400° for 9 minutes. Let cool for 3 minutes on pan and then move to a wire rack to cool completely.