Spread the pumpkin puree out on a plate and use a paper towel to blot the excess liquid out of it. This is important to stop the moisture from making the cookie dough too sticky and soft. Repeat with fresh paper towels until there is barely any liquid coming off of it and it looks dry and flaky, rather than watery and mushy.
Add the melted butter, both sugars, and blotted pumpkin puree to a large bowl and whisk together just until combined. You can use a stand mixer on low speed if you prefer, but it is not necessary.
Add the egg yolk and vanilla extract, and mix them in.
Sift the dry ingredients into a separate bowl, including the flour, baking soda, baking powder, salt, and spices. Mix them together, then add them to the main cookie dough and stir just until a soft dough forms and there are no more lumps of flour.
Chill the dough for 30 minutes to let the butter firm up.
Once the cookie dough has chilled, preheat the oven to 350°F / 180°'C (160° fan-assisted) and line a cookie sheet with parchment paper.
Scoop and roll the dough in your hands to make cookie dough balls - each ball should be about 2 tablespoons of dough. I like to use a cookie scoop for consistency. Optional - roll each ball in cinnamon sugar for some extra flavor and crunch.
Bake the pumpkin cookies for 11-14 minutes until they are golden brown and baked all over.
Remove from the oven and let them sit on the sheet for 10 minutes before moving to a wire rack to cool completely. I use a cookie lifter to transfer them without damaging them.
Notes
It is super important to blot the pumpkin puree fully before adding it to your cookie dough. Pumpkin contains a lot of moisture, and if we don't remove it it will make the cookies sticky and dense. Also, be sure to use canned pure pumpkin puree, not pumpkin pie filling or fresh pumpkin. See post above for more info.