Preheat the oven to 350 F. Line two baking sheets with parchment paper or silicone baking mats. Set aside.
Brown the butter in a saucepan over medium heat. The butter will melt, foam, then it will turn amber golden brown. When it smells nutty, remove from heat.
Pour the browned butter and any browned bits into a large mixing bowl.
Let the butter cool to room temperature. It should take about 25 minutes depending on the temperature of your kitchen. Don't chill the butter. It needs to be about 70F, but it shouldn't be solid or chilled.
Once the butter is at room temperature, whisk in the sugars until well-combined.
Whisk in the egg yolks, vanilla, and pumpkin puree until well-combined.
Add the flour, pumpkin spice, baking soda, and salt. Stir in just until combined. Don't overmix.
In a shallow dish, stir the sugar and cinnamon together until combined.
Using a medium cookie scoop (1.5 tablespoons), scoop up the dough.
Roll each ball of dough in the cinnamon-sugar mixture.
Place the scoops of dough 2 inches apart on the prepared baking sheets.
Bake for 8-11 minutes, or until the edges are set. The centers should look soft and slightly underdone in the cracks.
Let the cookies cool for about 10 minutes before removing to a wire cooling rack to finish cooling.
Notes
Butter: I use salted butter in this recipe. If you use unsalted butter, increase the salt to 1/2 teaspoon.
Brown sugar: Light brown sugar or dark brown sugar will work. Dark brown sugar will give you richer flavor.
Pumpkin puree: I recommend using canned pumpkin puree. If you're using homemade pumpkin puree, you may need to strain it to thicken it up before using. Be sure to use pumpkin puree, not pumpkin pie filling.
All-purpose flour: It's important to properly measure the flour. To do so either weigh it or sift/stir it to break it up. Then lightly spoon into the measuring cup and level.