In a medium bowl, combine the flour, brown sugar, baking powder and soda, salt, and spices.
In a large bowl, whisk egg yolks with buttermilk, pumpkin, and butter until smooth. Stir in dry ingredients until just combined.
In a mixing bowl with a whisk attachment, beat the egg whites on high until they hold very soft peaks. Gently fold into the waffle batter, until just combined.
Grease waffle iron lightly with spray and spoon batter into waffle iron. Cook according to manufacturer’s instructions. (I like to keep mine in the waffle iron 1-2 minutes longer to make sure the outside is crispy.)
Transfer waffles to rack in oven to keep warm and crisp. Continue with the remaining batter.