In a large bowl with a hand mixer, or in the bowl of a stand mixer with a paddle blade, beat together the butter and sugar until it’s light in color, about 2 minutes. Scrape down the sides of the bowl and the beater/blade.
Add the egg, egg yolk, and vanilla and beat until everything is well incorporated, about 2 minutes. Scrape down the sides of the bowl and the beater/blade.
Add the flour, cream of tartar, cinnamon, baking soda and salt and mix on low JUST until combined. The batter will be thick.
Using a cookie scoop, scoop two scoops of dough per cookie onto the baking sheet. Leave about 2-3” of space between each cookie. (If you’re using these USA baking pans and these silpat mats, you’ll get 12 cookies per pan.)
When you’ve scooped all the cookies, working with one at a time, roll the double scoop of dough into a ball using the palm of your hands. Roll the cookie dough in the cinnamon sugar so it’s coated well. Place it back onto the baking pan. Repeat the process for all the cookies.
Bake the cookies for 10 minutes. These cookies will puff up and not deflate much, so if you want a flatter cookie, use a pancake flipper to GENTLY press down on the cookies when you pull them out of the oven. Allow the cookies to cool on the baking pan for 10 minutes before placing them on a cooling rack to cool completely.
No cream of tartar? Can I substitute lemon? Not for this recipe. Using lemon juice will throw off the wet/dry ratio of ingredients and impart a lemon flavor that won’t work well with cinnamon. If you don’t have cream of tartar, I recommend these Shortbread Cookies or my Classic Sugar Cookie Recipe.