• Whisk together 2 ½ cups flour, 1 teaspoon baking soda, 2 teaspoons cream of tartar, ½ teaspoon cinnamon, and ¼ teaspoon salt in a bowl and set aside.

Now make the brown butter:

• Melt 2 sticks of 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.
• With an electric mixer, mix the melted butter and 1 ¼ cup packed brown sugar, ½ cup granulated sugar until thoroughly blended. Beat in 1 egg, 1 egg yolk, 1 teaspoon vanilla, and 1 Tablespoon yogurt until combined. Add the dry ingredients slowly and beat on low-speed just until combined.
• Chill your dough for 3 hours or as long as possible in the refrigerator (important!), You want the dough VERY cold. If you desire a ‘puffy’ cookie, place them in the fridge overnight.
• Preheat the oven to 350 degrees F. Once dough is chilled measure about 2 tablespoons of dough and roll into a ball. Meanwhile mix ¼ cup sugar and the 2 teaspoons cinnamon in a bowl. Roll balls in cinnamon-sugar mixture. Place dough balls on cookie sheet, 2 inches apart.
• Bake the cookies 8-10 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. Repeat with remaining dough.