Preheat oven to 350°. Spray donut pan with cooking spray and set aside.
Whisk together the flour, baking powder, salt, cinnamon and pumpkin pie spice in a large bowl and set aside. In another large bowl, whisk the melted butter and sugars together until smooth. Add in the pumpkin puree and vanilla and mix until completely smooth. Stir in buttermilk until combined. Pour in the flour mixture and mix until just incorporated being careful not to over mix so your donuts do not become tough.
Pour the batter into a ziploc bag and cut off one corner. This makes it much easier to pour into the donut rings. Pour batter into prepared donut pan about 3/4 to the top of each one. Bake for 14-16 minutes or until the tops are firm and spring back when you touch them.
While they are baking, mix up the cinnamon, pumpkin pie spice and sugar in a medium sized bowl and in another bowl, melt butter and set both aside. Remove donuts from oven and let them cool in the pan for 5 minutes or until firm enough to handle. You want them to still be very warm when coating them. If you use very hot donuts, you may not need to dip them into the butter if you prefer not to (the topping won't stick as well, but will stick somewhat). If using butter, quickly dip the tops of donuts into melted butter and then immediately into cinnamon spice sugar mixture. Place them on a wire rack before going onto the next. Repeat process for rest of the donuts.
Donuts are best served the same day but will stay fresh for up to 3 days if stored in an airtight container.
Do not cover until donuts are completely cooled and room temperature or the warmth from them trapped in the container will result in rubbery donuts.