To begin, place butter in a large microwave-safe mixing bowl. Melt for about 30 seconds, or until partially melted. Stir and set aside to cool.
In a separate bowl, stir together oats, flour, baking powder, baking soda, salt, and pumpkin pie spice.
Next, whisk together melted butter and both sugars. Then add vanilla and egg yolk to the sugar mixture. Add pumpkin puree and stir until just incorporated.
Combine the wet and dry ingredients and stir lightly until mixed.
Cover the dough with plastic wrap and chill in the fridge for 30 minutes.
Remove dough from fridge and preheat oven to 350℉.
Line a baking sheet with parchment paper and use a medium-sized cookie scoop to drop cookies onto the baking sheet. Carefully flatten cookies with the bottom of a glass tumbler (if desired).
Bake for 10 minutes. Remove from oven and cool for 5 minutes before transfering cookies to a cooling rack. Drizzle with salted caramel frosting and enjoy!