In a medium bowl, combine the buttermilk, pumpkin puree, light brown sugar, vegetable oil, egg, and vanilla extract. Whisk until smooth and creamy.

In a separate bowl, whisk together the all-purpose flour, pumpkin pie spice, baking powder, salt, and baking soda.

Gently fold the dry ingredients into the wet mixture until just combined. Aim for a thick batter.

Cover the bowl with plastic wrap and refrigerate the batter for at least 2 hours or overnight.

Melt the unsalted butter in a small skillet over medium heat and cook until golden brown, about 4 to 5 minutes.

Stir in the maple syrup, pumpkin pie spice, and salt into the browned butter. Boil gently for one minute, then add vanilla extract.

Preheat your waffle maker according to instructions and lightly grease it.

Pour the chilled batter onto the hot waffle iron and cook until golden brown and crispy, about 3 to 5 minutes.

Transfer the cooked waffles to a plate. Keep warm in a low oven while cooking remaining batter.

Top each waffle with chopped pecans and drizzle generously with the brown butter maple syrup.