Beat together softened butter and sugar.
Preheat oven to 375 degrees.
line baking sheet with parchment paper.
Add baking soda and cream of tartar and continue beating.
Add egg and vanilla and mix well.
Add flour and mix again until stiff dough forms.
Mix 4 Tbsp. sugar with 2 tsp. cinnamon in a small bowl.
By hand, form small pieces of dough into balls about 1 inch in diameter.
Roll balls in sugar mixture to coat.
Place balls about 2 inches apart on parchment-lined baking sheet.
Bake for about 11 minutes until cookies are set (tops should be crinkled).
Remove from oven and let sit on baking sheet for 2 minutes or so.
Use a spatula to gently remove to cooling rack.
When completely cooled, store cookies in covered tin or refrigerator.