For the cookies:
Whisk together the flour, baking soda, cream of tartar, cinnamon, and salt in a bowl and set aside. NOTE: Make sure your baking soda and cream of tartar are fresh!

Melt butter in a saucepan over medium heat. The butter will begin to foam. Make sure you whisk consistently during this process. After a couple of minutes, the butter will begin to brown on the bottom of the saucepan; continue to whisk and remove from heat as soon as the butter begins to brown and give off a nutty aroma. Immediately transfer the butter to a bowl to prevent burning. Set aside to cool for a few minutes.

With an electric mixer, mix the butter and sugars until thoroughly blended. Beat in the egg, yolk, vanilla, and yogurt until combined. Add the dry ingredients slowly and beat on low speed just until combined.

Chill your dough in the refrigerator (important!) until the dough is cold about 30-60 minutes, or place in freezer for about 20 minutes if you are super eager, although I cannot promise the same results if you do this. Fridge is always best! If you desire a puffier cookie, keep the dough in the fridge overnight.

Preheat the oven to 350ºF.

Once dough is chilled, measure about 2 tablespoons of dough and roll into balls. Meanwhile, mix the rolling mixture ingredients in a bowl. Roll balls in the cinnamon-sugar rolling mixture. Place dough balls on cookie sheet, 2 inches apart. If you desire a thinner cookie, flatten the tops of the cookies a tiny bit (very tiny) with your hand.

Bake the cookies 8-11 minutes or until the edges of the cookies begin to turn golden brown. They will look a bit underdone in the middle but will continue to cook once out of the oven. Bake longer if you like crispier cookies. Cool the cookies on the sheets at least 2 minutes. Remove the cooled cookies from the baking sheets after a few minutes and transfer to a wire rack to cool completely.