In a bowl, mix the butter and sugar together until creamed.
Mix in the egg and vanilla.
Stir in flour, baking soda, salt, cream of tartar, and cinnamon until just combined and form a ball. Do NOT overmix. You will notice this is a soft dough
Mix together the last 2 ingredients (1 tsp cinnamon & 1tsp sugar). Toss the ball of dough in the cinnamon to coat it
Place the dough in the center of the prepared cookie sheet into a tall ball (3 inches wide).
Bake for 14-16 minutes until the edges are browned. The center may appear undone but that's what you want. It will firm up. Allow to cool completely on the baking sheet. Enjoy!
Recipe Notes
*To get 1 Tbsp egg, crack egg into a small bowl, whisk until yolk and white are well blended, then measure out 1 Tbsp.