Preheat oven to 350 degrees F. Whisk together flour, cream of tarter, baking soda and salt; set aside.
With an electric mixer, beat butter and 1 1/2 cups sugar together until light and fluffy. Beat in eggs, one at a time. With mixer speed on low, add flour mixture, beating to combine.
In a shallow dish, combine 1/4 cup sugar and cinnamon. Form 1 inch balls (using about 1 tbsp of dough per cookie) and roll each in cinnamon sugar before placing on ungreased cookie sheets about 3 inches apart (these cookies spread significantly!).
Bake 8 to 10 minutes, until tops have crinkled and edges are set, but centres are still soft. Cool 3 minutes on baking sheet before transferring to wire racks to cool completely.
These cookies freeze wonderfully.