Preheat waffle maker: Plug in and preheat your Belgian or standard waffle iron according to manufacturer instructions. If you prefer ultra-crispy waffles, preheat your oven to 200°F (95°C) with a wire rack placed over a baking sheet.

Whisk dry ingredients: In a large bowl, whisk together all-purpose flour, brown sugar, baking powder, baking soda, cinnamon, pumpkin pie spice, and sea salt until thoroughly combined.

Mix wet ingredients: In a separate medium bowl, whisk together pumpkin puree, buttermilk, egg yolks, melted butter, and vanilla extract until smooth.

Whip egg whites (Pro-Tip for Maximum Fluffiness): In a clean small bowl, beat the 2 egg whites with a hand whisk or electric mixer until soft peaks form (about 2 minutes).

Combine batter: Pour the wet pumpkin mixture into the dry ingredients and stir gently with a spatula just until combined (a few small lumps are okay). Gently fold in the whipped egg whites in two batches until no white streaks remain.

Cook in waffle maker: Lightly grease the preheated waffle grids with melted butter or non-stick spray. Ladle approximately 1/2 to 2/3 cup batter (depending on waffle iron size) onto the center. Close lid and cook for 4 to 6 minutes, until steam stops escaping and the waffle is deep golden and crisp.

Serve hot & crisp: Transfer waffles immediately to the warm oven rack to keep them delightfully crisp while cooking remaining batter. Serve stacked warm with softened butter, generous pure maple syrup, and toasted pecans.