Simple sugar cookies with a tart taste rolled in cinnamon and sugar.
Preheat oven to 375°F and line two baking sheets with parchment paper.
In a mixer, cream butter, shortening, and sugar. Mix until light and fluffy. Add eggs and mix again.
Add flour, cream of tartar, baking soda, and salt. Mix until just combined.
In a small bowl, combine coating ingredients: sugar and cinnamon.
Form dough into one inch balls by rolling in your hand. Roll each ball in coating until it is completely covered. Place on the prepared baking sheets two inches apart. Bake in the oven for 8-10 minutes. You will want to see cracks along the top of the cookies. Allow to cool for 5 minutes and then transfer to a cooling rack to cool completely.