Preheat oven to 350º F. Grease a 10.25 inch cast iron skillet with butter or cooking spray if needed.
In a large mixing bowl, cream together the butter, sugar and brown sugar with an electric mixer, until smooth, 1-2 minutes.
Add in vanilla and eggs, mix until well combined.
In a separate mixing bowl whisk together flour, baking soda, cream of tartar, salt and cinnamon.
Add the dry ingredients mixture to the butter and continue to mix until a soft dough is formed, scraping down the sides of the bowl as needed.
In a separate bowl, mix together the remaining cinnamon and sugar.
Sprinkle the bottom of the cast iron skillet with half of the cinnamon sugar. Press the cookie dough evenly into the pan. Cover with more of the cinnamon sugar mixture, you might not use all of it, just use enough to liberally cover the top of the cookie.
Bake for 25-30 minutes, until the edges are golden brown. Allow to cool in the pan for 10 minutes before slicing or removing from the pan.
Notes
Nutrition facts are just an estimate of the listed ingredients.
Store any leftover cookie in an airtight container or zip top bag on the counter.