Preheat your oven to 375°F (190°C).
Prepare three baking sheets by lining them with parchment paper.
In a medium bowl, combine the flour, cream of tartar, baking soda, and salt.
Whisk together until well-mixed.
In a larger bowl, use a hand mixer or stand mixer to beat the softened butter until smooth.
Add the sugar and beat until the mixture is light and fluffy.
Add the eggs one at a time to the butter and sugar mixture, beating well after each addition.
Mix in the vanilla extract.
Gradually add the flour mixture to the wet ingredients, beating on low until just combined.
If the dough is too soft, chill it in the fridge for about one hour to firm up.
In a small dish, mix the sugar and cinnamon for the coating.
Form the dough into 1-inch balls and roll each ball in the cinnamon-sugar mixture.
Place the dough balls onto the prepared baking sheets, spacing them about 2 inches apart.
Bake for 8-10 minutes or until the edges are slightly golden.
Allow the cookies to cool on the baking sheet for a few minutes.
Then transfer them to a wire rack to cool completely.