Add the butter and both sugars to a bowl or bowl of a stand mixer. Cream together for about 1 minute.
Beat in the egg and vanilla.
Add in the dry ingredients, making sure to spoon and level the flour, don't scoop from the bag.
Scoop into balls using about 1 1/2 to 2 tablespoons of dough (I like these cookie scoops), then roll in the cinnamon sugar. Place on a baking sheet lined with parchment paper, then set in the fridge for at least 30 minutes, ideally 1 hour.
During the final 15 or so minutes, preheat the oven to 350 Fahrenheit.
The cookies will spread so I recommend only 6 on a baking sheet at a time. Bake for 10-14 minutes. They will continue to harden as they cool, so avoid over baking.
Let cool so they don't crumble, then enjoy!