In a large mixing bowl, beat butter till creamy and light in color.
Add 1 cup white sugar and ½ cup brown sugar, beat until fluffy.
Add eggs and continue to beat until smooth.
In a separate bowl, whisk together the flour, cream of tartar, baking soda and ½ Tablespoon cinnamon.
Add flour mixture to the creamed mixture, mix only until incorporated. Scoop sides of the bowl down with a rubber scraper.
In a small bowl, mix together ½ cup sugar and ½ Tablespoon cinnamon.
Roll dough into balls, then roll in the cinnamon sugar mixture. Place the balls on a baking sheet leaving plenty of room in between.
Flatten the balls just slightly so they do not roll. They will spread while baking. Place in freezer for 15 minutes.
Preheat oven to 350˚F
While waiting, continue to roll the other balls. Place them in the freezer as well.
Take out of freezer and bake 10 minutes. They will look puffed up, but they will settle once cool. Do not over bake them.
Using a scraper, push the edges of each cookie a bit towards the center. Allow cookies to cool slightly on the baking sheet before transferring to a baking rack. While still a bit warm, coat cookies with more cinnamon sugar if desired (highly recommended).