Remove excess moisture from the pumpkin: Line a plate with a few layers of paper towels. Spread the canned pumpkin out on top (don't spread it too thin or it will be difficult to transfer later). Blot the top with a paper towel or two, then let it rest for about 10 minutes. The moisture from the pumpkin will wick out onto the paper towels.
½ cup (120g) canned pure pumpkin puree
Combine dry ingredients: In a medium mixing bowl, whisk together the all-purpose flour, pumpkin pie spice, cinnamon, baking soda and salt. Set aside.
2 ½ cups (300g) all-purpose flour*, 1 tablespoon pumpkin pie spice, 1 teaspoon ground cinnamon, ½ teaspoon baking soda, ½ teaspoon salt
Melt the butter, either in a microwave-safe bowl in the microwave or in a pan on the stove.
¾ cup (170g) unsalted butter
Combine wet ingredients: Use an electric mixer (stand mixer or hand held mixer) to mix together the melted butter, brown sugar and granulated sugar until creamy. Add the pumpkin puree, egg yolk and vanilla and mix on medium-low speed until combined.
1 cup (200g) packed brown sugar, ¼ cup (50g) granulated sugar, 1 large egg yolk, 2 teaspoons vanilla extract
Add the dry ingredients to the mixing bowl in two parts, mixing on low speed until well combined. The dough will be very soft and slightly sticky.
Cover the bowl and chill the cookie dough in the refrigerator for at least 1 hour and up to 24 hours.
When you are ready to bake the cookies, preheat oven to 350° F. Line baking sheets with parchment paper.
Make cinnamon-sugar coating: Mix together the 1/4 cup granulated sugar and 1/2 teaspoon cinnamon in a small wide, shallow bowl.
¼ cup (50g) granulated sugar, ½ teaspoon ground cinnamon
Roll cookies: Use a small cookie scoop or spoon to scoop portions of dough and roll into 1-inch balls. (If the dough has been chilled overnight and is too firm to roll, let it sit at room temperature for about 10 minutes before rolling.) Roll the balls in the cinnamon-sugar and place on parchment paper lined baking sheets, about 3 inches apart.
Bake one pan of cookies at a time, for 9-11 minutes, until tops are set and bottoms are light golden brown. (The cookies may still be slightly puffy when you take them out of the oven and will flatten more as they cool on the baking sheet.)