In the bowl of your stand mixer fitted with the paddle attachment, beat the butter, granulated sugar and brown sugar on medium speed for 2 minutes.
Scrape the bowl down, and mix in the eggs and vanilla on low. The mixture will look lumpy.
In a separate bowl, whisk together the flour, corn starch, cream of tartar, baking soda and salt. Add the dry ingredients to the mixing bowl, and mix on low, just until combined. The batter will be very thick, and you'll need to use a spatula, or your hands, to incorporate all the flour at the bottom of the bowl.
Use a cookie scoop to divide the dough into 24 equal portions, about 1.5 ounces each. Roll each portion into a ball, then coat in the cinnamon sugar mixture. Refrigerate the dough balls for 1 hour.
Preheat the oven to 350 F, line a large baking sheet with parchment paper.
Place the chilled dough balls 3 inches apart on the baking sheet. Bake on the center oven rack for 11 1/2 - 12 minutes, until golden brown and set around the edges, but the centers are still slightly underdone. Cool on the pan for 2 minutes, then transfer to a cooling rack to cool completely.