Preheat your oven to 350°F (175°C).

In a mixing bowl, cream the unsalted butter and granulated sugar together until light and fluffy, about 3-4 minutes.

Add the eggs one at a time, mixing thoroughly after each addition.

In a separate bowl, whisk together flour, cream of tartar, baking soda, and salt, then gradually mix into wet ingredients until a soft dough forms.

In a small bowl, combine ground cinnamon and additional granulated sugar.

Scoop a tablespoon of dough, roll into a ball, then roll in the cinnamon-sugar mixture.

Place the dough balls on a baking sheet, spacing them apart.

Bake for 8-10 minutes until edges are set but centers are still soft.

Cool on baking sheet for a few minutes before transferring to a wire rack.