Preheat oven to 375°F. Line baking sheets with parchment paper.
Cream butter and sugar until light and fluffy.
Beat in eggs and vanilla until smooth.
Add flour, baking soda, and cream of tartar; mix just until combined.
Scoop dough into large 3-tablespoon portions and roll into balls.
Roll each ball in cinnamon sugar.
Place on baking sheet about 2 inches apart.
Bake 9–10 minutes, until edges are set and centers are soft and slightly underdone.
Let cookies cool on the pan for a few minutes before transferring.
