makes 22
Using the paddle attachment on an electric mixer, cream the butter and sugars. Mix in the egg yolk, pumpkin, pumpkin pie spice, and vanilla, stop mixer to scrape down the sides with a spatula. Mix in the flour, baking soda, and salt. Chill dough for at least 1 hour, the longer the better, ideally overnight.
Preheat oven to 375°. Scoop dough by heaping tablespoon and place 8 on a rimmed cookie sheet lined with parchment or a Silpat. Sprinkle tops with a pinch or two of cinnamon sugar. Bake for 14 minutes, until fragrant with lightly browned edges.