Special equipment: a 1 1/2-tablespoon cookie scoop
Preheat the oven to 400 degrees F and line several baking sheets with parchment paper.
In a large bowl, whisk together the flour, cream of tartar, baking soda and salt. Set aside.
In the bowl of an electric mixer, cream the butter and 1 1/2 cups of the sugar together until light and fluffy, 3 to 5 minutes. Then beat in the eggs and scrape the bowl. Turn the mixer to low and slowly add the flour mixture until well combined.
Mix the remaining 1/4 cup sugar and cinnamon together in a small bowl. Use a 1 1/2-tablespoon cookie scoop to measure out the dough balls. Roll each ball in your hands to even out, then roll in the cinnamon sugar to thoroughly coat.
Place the balls on the prepared baking sheets, 2 1/2 inches apart. Bake until just golden around the edges, 8 to 9 minutes. Cool for several minutes on the baking sheets before moving.