In a medium bowl, mix flour, cream of tartar, baking soda and salt, set aside
In a large bowl, with an electric mixer, beat butter and shortening, until creamy. Add 1 ½ cups sugar and continue beating until fluffy. Add eggs one at a time and mix well. On low-medium speed, mix in dry ingredients, one cup at a time, until blended.
Chill the dough for 30-60 minutes.
CINNAMON SUGAR: In a small bowl, mix 3 tablespoons sugar and cinnamon together.
Shape dough by rounded teaspoonfuls into balls. Roll dough balls in cinnamon sugar.
Place about 2 inches apart on an un-greased or parchment lined baking sheet. Flatten slightly with the palm of your hand. Bake 8 to 10 minutes or until set. Immediately remove from baking sheet. Cool completely on wire rack, before storing in airtight containers.