Sourdough Discard Snickerdoodles

Combine the sugar and cinnamon in a medium bowl. Preheat oven to 375 degrees.
Combine the flour, cream of tartar, baking soda, cinnamon, and salt in a medium bowl and set aside.
In the bowl of a stand mixer fitted with the paddle attachment, cream together the butter and sugar, scraping down the sides as needed. Once light and fluffy, add the egg and discard and mix to combine. Add the dry ingredients in three increments, mixing after each addition. Once all the dry ingredients have been mixed in, roll the dough into 35 gram balls (roughly 1 ½ tablespoon each).
Roll the balls through the cinnamon sugar to coat and arrange on parchment-lined baking sheets. Bake 7-9 minutes, until tops are domed and beginning to set. Let cool on baking sheet for 2 minutes, then transfer to wire rack to cool completely.