Brown your butter over medium heat. Stir occasionally until the butter starts to foam, then stir constantly. Once browned, transfer your butter to a heat-proof bowl and place in the freezer to cool for 10-15 minutes.
While your butter is cooling, prepare your dry ingredients in a medium bowl. To the bowl, add your flour, cream of tartar, cinnamon, salt, and baking soda. Mix until combined.
When your butter has cooled to room temperature, add it to a large mixing bowl along with your granulated sugar, whole egg, and egg yolk. Whisk until thoroughly combined. Make sure there's no more streaks of egg!
Add your dry ingredients to the wet ingredients and mix with a rubber spatula until there's no more flour visible.
Scoop your dough into 3 Tablespoon size balls. You should end up with 10-12 balls.
In a small bowl, combine 2 teaspoons of cinnamon with 25g (1/4 cup). Roll each dough ball in the cinnamon sugar mixture until well coated.
Place the dough balls on a tray or plate that will fit in your freezer. Freeze for two hours.
Preheat your oven to 350F. Bake cookies at 350F for 9-11 minutes or until the cookies no longer look wet on top. You want to under bake them slightly because they'll continue to cook on the tray.