Preheat oven to 400° and line a baking sheet with parchment paper. Set aside.
In a medium bowl, whisk flour, cream of tartar, baking soda and salt together. Set aside.
In a large bowl, beat butter and sugars together until creamy.
Add egg and yolk, beat until combined.
Gradually add flour mixture into sugar mixture beat after each addition until combined.
Using a teaspoon, drop rounded 1" ball into cinnamon sugar mixture to coat then place on prepared baking sheet.
Bake for 7 minutes, remove from oven, let cookies sit on baking sheet for 5 minutes then transfer to wire rack.
Recipe adapted from Allrecipes