Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.

In a large bowl, cream together the softened butter and sugar until light and fluffy.

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

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

Gradually add the dry ingredients to the butter mixture, stirring until just combined.

In a small bowl, mix the extra sugar and cinnamon for rolling.

Form the dough into 1-inch balls and roll them in the cinnamon-sugar mixture.

Place the coated balls on the prepared baking sheet, spacing them about 2 inches apart.

Bake in the preheated oven for 10-12 minutes or until the edges are lightly golden.

Remove from the oven and let cool on the baking sheet for a few minutes before transferring to wire racks to cool completely.