Preheat the oven to 400 degrees F and line your baking sheets with parchment paper.
In the bowl of an electric mixer, cream the butter, vegetable shortening, and sugar until it is light and fluffy. Then beat in the eggs, one at a time, until everything is well combined.
Turn your mixer on low and slowly sift in the flour, cream of tartar, baking soda, and salt. Mix to combine.
In a small bowl stir together the granulated sugar and cinnamon for the coating.
Using a 1 ½ tablespoon cookie scoop measure out the dough balls. Roll each ball in he cinnamon and sugar mixture to thoroughly coat. Roll each ball in your hand to even them out.
Place the balls on your prepared baking sheets with at least 2 ½ inches between each of them. Bake until golden brown around the edges, about 8 minutes. Allow the cookies to cool on the baking sheet for a minute and then transfer to a cooling rack.
