In one bowl, sift together flour, cream of tartar, baking soda, and salt. Using a hand mixer, beat together butter and part of the sugar in another bowl until light and fluffy. Continue beating in eggs until well blended. Mix the flour mixture into the butter mixture until smooth and incorporated. Refrigerate the dough for approx. 1 hr. or until chilled and firm.
Combine sugar and cinnamon in a bowl. Using an ice cream scoop, scoop out thick mounds of dough. Roll each in the mixture of sugar and cinnamon. Transfer to a baking sheet and leave room for each cookie to spread out while baking. Bake at 180°C/350°F for approx. 8-11 min. in the upper part of the oven, until golden brown. Let them cool down for approx. 2 min. before transferring to a wire rack to finish cooling. Enjoy!