Preheat oven to 350℉ and line a baking sheet with parchment paper.
In a large bowl, whisk together Member's Mark™ All-purpose Flour, baking soda, cream of tartar, Member's Mark™ Ground Cinnamon, and salt. Set aside.
In the bowl of a stand mixer fitted with the paddle attachment, or a large bowl if using a handheld mixer, beat together Member's Mark™ Unsalted Sweet Cream Butter and Member's Mark™ Granulated Sugar until soft and fluffy.
Add the egg, egg yolk, and vanilla extract and beat until combined, scraping down the bottom and sides of the bowl if necessary.
Add the dry ingredients to the wet ingredients and mix until combined. Do not over-mix.
For the cinnamon sugar: combine Member's Mark™ Granulated Sugar and Member's Mark™ Ground Cinnamon in a small bowl.
Use a ¼ cup measuring cup to scoop the dough. Roll the dough balls in the cinnamon sugar mixture so they are evenly coated.
Place on the prepared baking sheet and bake for 12-14 minutes.
Let the cookies cool on the baking sheet for 5 minutes, then transfer to a cooling rack to cool completely.