Preheat the oven to 350F degrees. Line cookie sheets with parchment paper or silicone baking mats.
In a large bowl beat together the butter and 1 1/3 cup granulated sugar until fluffy.
Beat in the egg, egg yolk and vanilla.
In a medium bowl whisk together the flour, corn starch, cream of tartar, baking soda and 1 tsp cinnamon.
Slowly beat the flour mixture into the butter mixture about 1/2 at a time until combined.
On a plate or in a shallow bowl, stir together the 3 tbsp granulated sugar and 1 tbsp cinnamon.
Form the cookie dough into balls about 1 tbsp in size, roll in cinnamon sugar, and place 2 inches apart on the cookie sheet.
Bake for 7-9 minutes, or until the tops look set. Baking longer will create crispier cookies.