Making The Pumpkin Donuts
In a large bowl, combine 4 tablespoons melted butter, brown sugar, egg, and vanilla extract. Mix well until fully blended. Blot the pumpkin puree with paper towels to remove excess moisture. Add the pumpkin puree and buttermilk to the wet mixture and stir until smooth.
In a separate medium bowl, whisk together flour, baking powder, baking soda, salt, and pumpkin pie spice until evenly combined.
Add the dry ingredients to the wet ingredients and mix until a smooth batter forms.
Spoon the batter into a silicone donut hole pan, mini muffin pan, or egg bite pan, filling each cavity with about a tablespoon of batter. Using a small cookie scoop can help for even portions. Wipe any drips off the pan edges.
Preheat an air fryer to 350 degrees on the air fry setting. Bake the donuts in the air fryer for 6-8 minutes or until golden brown. Remove and allow to cool slightly, then transfer the donut holes to a wire rack. Repeat the process with the remaining batter. See notes for baking in a conventional oven.

Adding The Cinnamon Sugar Coating
Pour 1/2 cup melted butter into a small bowl. In another bowl, mix sugar and cinnamon until combined.
Once the donut holes have cooled enough to handle, dip each first in the melted butter, then roll in the cinnamon sugar mixture to coat evenly.

For The Cream Cheese Frosting Dip (optional)
In a medium bowl, beat softened cream cheese and powdered sugar until smooth. Add vanilla extract and 4 tablespoons of milk, continuing to beat until creamy. If the frosting dip is too thick, add an additional tablespoon or two of milk until desired consistency is reached. Serve as a dip for the donuts and enjoy!