Adjust oven rack to middle position and preheat oven to 375F degrees. Line two baking sheets with parchment paper or a silicone mat.
In a medium bowl, whisk together the flour, cream of tartar, baking soda, and salt.
Using the stand mixer fitted with the paddle attachment, beat the butter and sugar on medium speed until light in color and fluffy - about 2-3 minutes.
Add the eggs, one at a time, mixing until incorporated after each, and scraping down the sides of the bowl as needed. Then add the vanilla extract and mix until combined.
Reduce the mixer speed to low and slowly add the flour mixture until combined. Give the mixture a final stir by hand to make sure that all the flour is mixed in. Place the dough in the refrigerator and chill for at least 20 - 30 minutes.
In a small shallow dish, combine the 1/4 cup of sugar and cinnamon.
Using a small cookie scoop or your hands, form the dough into 1 tablespoon dough balls, rolling each through the sugar mixture until well coated. Place on the prepared baking sheets 2 inches apart.
Bake the cookies one sheet at a time, until the edges begin to turn golden brown and the centers are still soft and puffy - and will even look a bit under-baked. About 10 - 12 minutes. For crispier cookies, bake for a couple minutes longer.
Let cookies cool on the baking sheet for about 2-3 minutes then move to a cooling rack to cool completely. Enjoy!