Preheat oven to 350 degrees, place rack in center of the oven.
For topping, mix 1/4 cup sugar and 2 teaspoons cinnamon together in a small bowl. Set aside.
In the bowl of a stand mixer or large bowl, place the butter, dark brown and granulated sugar. Beat until smooth.
Add the pumpkin, egg, one egg yolk, and vanilla, beat on medium speed, scraping down the sides and bottom of the bowl one time during mixing.
Add all of the dry ingredients to the bowl at one time, mix on low until the wet and dry ingredients are incorporated. Or fold together using a spatula.
Using a cookie scoop or a spoon, form 2 inch balls of dough and roll in cinnamon sugar mixture. Place on a lightly greased cookie sheet or on a parchment lined cookie sheet. Barely flatten the cookie dough ball with the palm of your hand.
Bake at 350 degrees for 10-12 minutes or until the top is set and the cookie does not have any wet appearance on top. Remove from oven and let cool.