1. Heat oven to 375 degrees F. Line a large cookie sheet with parchment paper or silicone baking mats (always recommended for cookies). Set aside.

Topping

1. Combine the granulated sugar and cinnamon together in a small bowl. Set aside

Batter

1. Whisk the flour, cream of tartar, baking soda, cinnamon and salt together in a medium bowl.
2. In a large bowl using a hand mixer beat the butter and granulated sugar together on high speed until smooth and creamy, about 2 minutes.
3. Add the egg, egg yolk and vanilla extract. Beat on medium-high speed until combined, scraping down the sides and bottom of the bowl. With the mixer on low speed, slowly add the dry ingredients to the wet ingredients in 3 different parts. The dough will be thick.
4. Roll cookie dough into balls, about 1 1/2 tablespoons of cookie dough. Roll the dough balls in cinnamon-sugar topping. Place 3 inches apart on the baking sheet.
5. Bake cookies for 10 minutes. The cookies will be very puffy and soft. When they are still very warm, lightly press down on them with the back of a spoon or fork to help flatten them out. Allow cookies to cool on the baking sheet for 10 minutes and transfer to a wire rack to cool completely.