Mix butter, sugar, and eggs in a stand mixer on high until the mixture is pale and fluffy, about 1-2 minutes. Sift in the flour, cream of tartar, baking soda, and salt. Blend until dough comes together.
In a separate small bowl, mix together the cinnamon and sugar. Shape the dough into 1" balls and roll them in the cinnamon and sugar mixture until completely covered. Place three per row on a cookie sheet, about 2 inches apart. Make four rows for a total of 12 cookies.
Bake on 350°F for 9-10 minutes. Allow them to cool for a couple minutes, then serve warm with a large glass of milk. Enjoy!