Preheat your oven to 350°F (175°C).

In a large mixing bowl, whisk together the flour, cream of tartar, baking soda, and salt until well combined.

In a separate bowl, use an electric mixer to cream together the softened butter, granulated sugar, and brown sugar until the mixture is fluffy and light in color.

Beat in the eggs one at a time, ensuring each is fully incorporated, then stir in the vanilla extract.

Gradually add the flour mixture to the wet ingredients, mixing gently until a dough forms.

In a small bowl, combine the cinnamon and 3 tablespoons of sugar.

Roll the dough into 1-inch balls, coating each in the cinnamon-sugar mixture.

Place the dough balls on a baking sheet lined with parchment paper, spacing them about 2 inches apart.

Bake for 8-10 minutes, or until the edges are golden and the centers remain soft.

Let the cookies cool on the baking sheet for a few minutes before transferring them to a wire rack to cool completely.