Preheat oven to 350 F. In a large bowl add the softened butter, brown sugar, and sugar. Mix well with a hand mixer or stand mixer until the sugar is well blended into the butter.
½ cup butter, ¼ cup brown sugar, ⅓ cup sugar
Add the pumpkin puree, egg, and vanilla extract to the bowl and mix well to incorporate.
2 tablespoon pumpkin puree, 1 egg room temperature, 2 teaspoon vanilla extract
Add the oat flour, baking soda, and sea salt to the bowl and gently mix into the dough. You can use a mixer on low speed for this or a rubber spatula. Be sure not to overmix this step and only mix until no flour clumps remain.
1 ⅔ cup oat flour, ½ teaspoon pumpkin spice, ½ teaspoon baking soda, ½ teaspoon sea salt
In a shallow bowl, mix together the sugar and cinnamon.
¼ cup sugar, 1 tablespoon cinnamon
Use a large cookie scoop to scoop the dough and gently roll into a ball shape with your palms. Roll the dough in the cinnamon sugar until coated. Then place on a parchment paper lined baking sheet. Leave at least 2 inches between each cookie so they have room to spread in the oven. Repeat with remaining dough.
Bake for 11 - 13 minutes until the edges are golden brown and the centers of the cookies are slightly set.
While the cookies are still warm, use a large circular cookie cutter to form the cookies into a perfect circle or use a fork to gently press the edges of the cookie towards the center. This is optional but helps to create a perfectly circular shape.
Once cool, enjoy or store in an airtight container or cookie jar. They will keep for up to a week out on the counter.