Preheat oven to 400 degrees. Line a large baking sheet with parchment paper. Set aside.

In a medium bowl, stir together flour, cream of tartar, baking soda and salt.

In the bowl of a stand mixer, combine butter and 3/4 cup sugar. Beat until light and fluffy, about 4 minutes. Add egg and beat until well combined, scraping down the sides of the bowl as needed. Gradually add flour mixture and mix until combined.

In a small shallow bowl, combine remaining 1/4 cup sugar and cinnamon. Shape dough into 1-1 1/2 inch balls. Dip the balls into the sugar mixture coating thoroughly. Place on prepared sheet 2 inches apart.

Bake 8-10 minutes until golden brown. Cool on sheet then transfer to wire rack.