Pre-heat oven to 375° F. Line two large cookie sheets with parchment paper or baking mats (set aside).
Make the Topping: Combine the granulated sugar and cinnamon together in a small bowl.
Make the cookies: Whisk together the flour, cream of tartar, baking soda, cinnamon and salt together in a medium bowl.
In a large bowl using a hand mixer and stand mixer fitted with a paddle attachment, beat the butter and granulated sugar together on high speed until smooth and creamy, about 2 minutes. Add the egg, egg yolk, and vanilla extract. Beat on medium-high speed until combined. Scrape down the sides and up the bottom of the bowl with a rubber spatula as needed. With the mixer running on low speed, slowly add the dry ingredients to the wet ingredients in 3 equal parts. The dough will be thick.
Roll cookie dough balls, about 1.5 Tablespoons of cookie dough each. Roll the dough balls in cinnamon-sugar toppings. Sprinkle extra cinnamon-sugar on top if desired. Arrange 3 inches apart on baking sheets.
Bake the cookies for 10 minutes. The cookies will be very puffy and soft. You can flatten them with the back of a spoon if you like when warm as the author recommends. I leave mine puffy. All the cookies to cool on the baking sheet for 10 minutes and then move to a wire rack.
The cookies remain soft and fresh for 7 days in an airtight container at room temperature.