To the bowl of a stand mixer fitted with the paddle attachment (or large mixing bowl and electric mixer) combine the butter, sugars, and beat on medium-high speed until creamed and well combined, about 3 minutes.

Stop, scrape down the sides of the bowl, and add the egg, vanilla, and beat on medium-high speed until well combined, light and fluffy, about 3 minutes.

Stop, scrape down the sides of the bowl, and add the add the flour, baking soda, cream of tartar, optional salt, and beat on low speed until just combined, about 1 minute.

Using a medium 2-inch cookie scoop or your hands, form approximately 14 equal-sized mounds of dough (2 heaping tablespoons each), roll into balls, and flatten slightly.

Place mounds on a large plate or tray, cover with plasticwrap, and refrigerate for at least 1 hour, up to 5 days. Do not bake with unchilled dough because cookies will bake thinner, flatter, and be more prone to spreading.

Preheat oven to 350F, line a baking sheet with a Silpat or spray with cooking spray.

In a small bowl, combine sugar, cinnamon, and stir to combine.

Dredge each mound of dough through cinnamon-sugar.

Place dough mounds on baking sheet, spaced at least 2 inches apart (I bake 8 cookies per sheet) and bake for about 9 minutes, or until edges have set and tops are just set, even if slightly undercooked, pale, and glossy in the center; don’t overbake for soft, pillowy cookies. For firmer cookies, bake a minute or two longer. Cookies firm up as they cool.

Allow cookies to cool on baking sheet for about 10 minutes before serving. I let them cool on the baking sheet and don’t use a rack.