Preheat oven to 375°F and line baking sheets with parchment.

Whisk flour, cream of tartar, baking soda, and salt together.

Beat butter and 1 1/2 cups sugar until fluffy, add eggs and vanilla, then stir in flour mixture.

Mix 3 tablespoons sugar and cinnamon together in a small bowl.

Roll dough into 1 1/2-inch balls and roll each ball in cinnamon sugar to coat.

Place on prepared sheets 2 inches apart and bake 9-11 minutes until edges are just set.

Cool on pan 5 minutes — they firm up as they cool.