In a medium bowl, sift the flour, baking soda, salt, cinnamon, pumpkin pie spice, and nutmeg. Add in the oats. Set aside.
1 3/4 cups All-purpose flour, 1 1/2 cups Old fashioned oats, 1 tsp Baking powder, 1 tsp Salt, 2 tsp Ground cinnamon, 2 tsp Pumpkin pie spice, 1/4 tsp Ground nutmeg
Spread the pumpkin puree on a dinner plate. Use 8 sheets of paper towels, using two at a time, press on the pumpkin to absorb the moisture. Do this 4 times.
1 cup Pumpkin puree
In a large bowl, mix the melted butter, sugar, brown sugar, vanilla, pumpkin puree, and egg yolk. Mix using a whisk.
1 cup Unsalted butter, 3/4 cup White granulated sugar, 3/4 cup Brown sugar, 1 tsp Pure vanilla extract, 1 Egg yolk
Add in the dry ingredients and mix using a baking rubber spatula. Mix until just combined.
Preheat the oven to 350℉. Line two cookie sheets with parchment paper. Let the cookie dough rest for 10 minutes before scooping. Pour the white granulated sugar into a bowl.
1/3 cup White granulated sugar
Using a small cookie scoop, scoop the dough. Roll each cookie dough ball into the sugar. Place 12 cookie dough balls per cookie sheet. Use your fingers to slightly flatten the cookie dough balls. When flatten it will equal to 2 1/2 inches in diameter.
Bake for 10-12 minutes. Bake until the cookie look set in the middle. Since they are pumpkin cookies, they won't be golden brown on the edges like other cookies.
Let the cookies sit on the hot pan for 4 minutes before transferring to a cooling rack to cool completely.