Preheat your oven to 375°F (190℃). Line several baking sheets with parchment paper.
In the bowl of a electric stand mixer (see note below) fitted with the paddle attachment, cream the sugar, butter, brown sugar and vanilla on medium speed until light and fluffy, about 4 to 5 minutes. With the mixer on low, add in the eggs one at a time, taking care to fully blend the first before adding the second. Scrape the sides and bottom of the bowl to make sure everything is incorporated. Add in the cream of tartar, baking soda and salt and mix 1 minute more. Add the flour and mix until until just barely combined.
To make the cookie coating, in a small bowl whisk together the granulated sugar and cinnamon.
Use a 2-tablespoon cookie scoop (if you have one) to portion out the cookie dough balls. Give the dough ball a generous coating of cinnamon-sugar mixture and and set on the baking sheet, allowing 2 inches (5 cm) of space between dough balls. Sprinkle any remaining cinnamon sugar over the tops of the dough balls.
Bake in the center of the oven for 11 minutes. Use the edge of a spatula to nudge any misshapen cookies back into shape. Let the baked cookies cool on the cookie sheet, set over a wire rack. Enjoy the best snickerdoodles! xx
