Preheat your oven to 350°F (175°C) and prepare baking sheets lined with parchment paper.

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

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

In a separate bowl, whisk together the flour, cream of tartar, baking soda, and salt.

Combine the wet and dry mixtures gently until no dry flour remains.

Cover the dough with plastic wrap and refrigerate for at least 1 hour.

Mix the sugar and cinnamon together for coating.

Shape dough into one-inch balls and roll them in the cinnamon-sugar mixture.

Place the balls on the baking sheets, spaced about 2 inches apart.

Bake for 9-11 minutes or until edges are golden and centers are slightly underdone.

Cool on the baking sheets for 2-3 minutes before transferring to a wire rack.