Preheat your waffle iron.
In a large bowl, whisk together the flour, sugar, baking powder, baking soda and salt, and the spices. Set aside.
To a separate bowl, add the melted butter, buttermilk, pumpkin, egg yolks, and vanilla. Whisk well to combine.
Add the egg whites to a separate bowl and mix on high speed with a hand mixer or stand mixer until they reach the hard peaks stage (when you remove the mixer from the egg whites they form peaks that don't fall). If you're short on time, feel free to mix the eggs whites in with the butter, buttermilk, yolks and vanilla instead of whipping them separately.
Add the dry ingredients to the wet ingredients and mix well with a silicone spatula, scraping down the sides of the bowl.
Add the whipped egg whites, a little at a time, and fold them into the batter gently just until all the egg whites have been incorporated.
Brush the waffle iron with oil or spray it with cooking spray.
Ladle about 1/2 cup of batter into the waffle iron for each rectangular waffle, and more if you're making round waffles. This recipe makes approximately 4 round Belgian-style waffles or 12 smaller square waffles.
Cook according to your waffle iron's instructions (every waffle iron is different), or until the waffles are golden brown. Repeat until all the batter is gone.
Serve immediately with whipped cream, maple syrup, or your favourite waffle toppings.