In a large skillet brown the butter. It will first melt, then it will bubble and sizzle, then it will start to foam. Use a rubber spatula to stir during this process. Once your butter has deep golden brown all over the bottom, remove from heat and let cool for about 15 minutes.

While your butter cools, in a medium mixing bowl combine the flour, baking soda, cream of tartar, cinnamon, and salt.

In the bowl of a stand mixer fitted with a paddle attachment or in a large mixing bowl using a hand mixer pour the brown sugar and sugar.

Once the butter is done cooling, pour the butter over the sugars and mix for 1-2 minutes. Add the eggs, vanilla, and Greek yogurt or sour cream and stir till mixed well.

Add the dry ingredients in and mix till just combined.

Put in fridge for at least 3 hours or up to 2 days. If you leave them in the fridge at least 12 hours, your cookies will be less flat.

Preheat oven to 350F and line 2 baking sheets with parchment paper.

Remove dough form fridge and mix 1/4 cup sugar and 2 teaspoons cinnamon together.

Roll dough into about 2 tablespoon sized dough balls, roll in cinnamon sugar, then place on baking sheet.

Bake for 8-12 minutes till the edges start to get golden brown. The middle may look under cooked still but the cookies will continue to cook on sheet out of oven. Let the cookies sit on the baking sheet for 5 minutes before removing to a wire cooling rack.