In a stainless steel pan, add the cubed butter and place it over medium heat. Stir the butter occasionlly until it looks foamy, smells nutty, and the bottom is covered in amber brown bits.
Take the pan off the heat and pour the butter into a large bowl. Make sure to scrape all of the butter and browned bits from the pan with a rubber spatula. You should have about 170 g or ¾ cup browned butter.
Let the browned butter cool for about 20 minutes, or until it feels room temperature.
Whisk the brown and white sugar into the butter.
Whisk in the egg, egg yolk, and vanilla.
Use a rubber spatula to fold in the flour, baking soda, salt, and cream of tartar until just combined.
Cover the bowl with plastic wrap and place it in the fridge to chill for 30 minutes.
In a small bowl, mix together the sugar and cinnamon.
After chilling, scoop the dough into 3 tablespoon (66 g) sized portions and roll them in the cinnamon sugar. Place them on a lined baking tray and place them back in the fridge for at least another 30 minutes (or overnight for the best flavor!).
Then preheat the oven to 350 F/180 C.
Bake the cookies spaced 2-3 inches apart for 9-10 minutes, or until the edges are a light golden brown and the middle is puffy.If baking the next day, they may need to bake 1-2 minutes longer in the oven. Let cool completely on a wire cooling rack then enjoy!