whisk together the flour, baking soda, cream of tartar, 1/2 teaspoon cinnamon, and salt. set aside

melt butter in a saucepan over medium heat. the butter will begin to foam. make sure you whisk constantly 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. you want a rich brown color. immediately transfer the butter to a bowl to prevent burning. set aside to cool for a few minutes

with a mixer, mix butter, brown sugar, and 1/2 cup sugar until well mixed

add egg, yolk, vanilla, and yogurt. mix well

add dry ingredients slowly (1/4 cup at a time) and mix on low speed just until combined

chill dough for at least 3 hours in the fridge (important step)

preheat oven to 350

once dough is chilled, measure about 1 tablespoon of dough and roll into a ball

mix 1/4 cup sugar and 2 teaspoon cinnamon in a bowl

roll dough balls into cinnamon sugar mixture

place balls on a cookie sheet

bake 8-11 minutes or until edges of cookies begin to turn golden brown (bake longer if you want crispier cookies)

remove from oven and let cool on the sheet for 2 minutes

remove from sheet and set on wire rack to cool completely

enjoy :)