Preheat oven to 350F. Grease either a 9x9. (Depending on how thick you want them to be)

Whisk together the flour, cream of tartar, baking soda, and salt; set aside.

Cream butter and sugar until light and fluffy. Add egg. Gradually add flour mixture. Spread into pan.

Combine sugar and cinnamon in a small bowl; sprinkle over dough.

Bake at 350F for 14-18 minutes, or until golden brown (or a toothpick inserted near center comes out clean). Let cool in pan. Cut into bars.