In a big bowl, lightly whisk the flour, baking powder, baking soda, salt, pumpkin pie spice, and nutmeg together.
In another bowl, whisk the eggs and brown sugar together until any lumps are dissolved and well blended.
Add in pumpkin puree, butter, buttermilk, and vanilla; whisk until smooth; add to the flour mixture and blend until smooth.
Preheat oven to 200°; heat a waffle iron according to manufacturer’s directions; lightly grease it with a pastry brush dipped in a little oil.
Pour in enough batter just to fill the iron and spread it evenly, then close the waffle iron.
Cook until the waffle iron opens easily and the waffles are golden brown on the outside and cooked through inside.
Remove to a platter and keep warm in the oven while you cook the remaining waffles.
Serve waffles sprinkled with powdered sugar and drizzled with maple syrup.
*OAMC—waffles can be frozen for 1 month; reheat in a 350° oven until warmed through, about 15 minutes.