Heat a medium saucepan or skillet over medium heat, add butter. Stir often and watch carefully as butter starts to melt and turn a golden color. Watch for brown bits to form along edge of pan and the butter start to turn frothy. Once it turns a gold color, remove from heat and let cool for 5 minutes.

In a large mixing bowl, add dark brown sugar and sugar. Carefully pour in melted butter. Cream for 4-5 minutes.

Add 1 egg, 1 egg yolk, and vanilla and cream for 1 minute.

Add cinnamon, flour, cream of tartar, baking soda, and salt.

Form the dough into a ball and cover with plastic wrap. Chill for at least 30 minutes or preferably overnight.

Once you are ready to bake, preheat oven to 350 degrees. In small bowl, stir together sugar and cinnamon. Roll cookie dough into a desired size ball. Roll each cookie dough ball in the cinnamon sugar mixture and double coat it.

Place cookies on parchment or silpat lined cookie sheets.

Bake for 8-11 minutes. Allow to cool for several minutes before moving to cooling racks.