Preheat oven to 375°F. Line baking sheets with parchment paper or silicone mats; set aside.
Sift (or whisk) flour, salt, baking soda and cream of tartar into a medium mixing bowl; set aside.
Cream together butter and sugar with an electric mixer on medium speed until light and fluffy (about 3-6 minutes). Beat in the eggs, one at a time, until incorporated (about 30 seconds), scraping down the bowl as necessary. Add vanilla extract and mix to combine.
Reduce the mixer speed to low and gradually add the flour mixture until combined (about 30 seconds). Give the dough one more stir by hand to make sure that all of the ingredients are completely mixed together.
If time allows, cover the bowl and chill the dough in the refrigerator for about 30 minutes. This isn't necessary, but it yields thicker cookies that spread less in the oven.
Combine the sugar and cinnamon for the topping in a small bowl.
Using damp hands, roll about 2 tablespoons of dough at a time into balls, then roll in the cinnamon sugar topping to coat. Arrange the dough on the prepared baking sheets, spaced about 3 inches apart.
Bake the cookies for about 10-11 minutes, or until just lightly brown around the edges but still soft and puffy in the center. Let the cookies cool on the baking sheet for 10 minutes, then transfer to a wire rack to cool completely.