In a medium bowl, whisk the all-purpose flour, cream of tartar, baking soda, cinnamon, and salt. Set aside.

In a large bowl, take the softened unsalted butter and granulated sugar and cream together with a hand mixer. It will take about 2 minutes on medium speed. Scrape the sides of bowl of down as needed.

Slowly pour the dry ingredients into the wet ingredients beating on low until fully incorporated. The batter will be thick.

Whisk the granulated sugar and cinnamon in a small bowl.

Roll the snickrdoodle batter into small bowls then roll them around in the cinnamon sugar coating and place onto a baking sheet lined with parchment paper. The cookies will spread so leave about 3 inches between each cookie.

Bake in the oven 11-12 minutes at 375℉/190℃/Gas Mark 5.

Remove from the oven and press down on the top of each cookie with the back of a small spoon for the signature cracked look.

Let cool on the tray for 5-10 minutes then remove the cookies from the sheet and place onto a cooling rack to continue to let cool.