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

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

Gently fold the dry mixture into the wet ingredients until just combined, leaving some small lumps.

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

In a small skillet, melt unsalted butter over medium heat until golden brown. Add maple syrup, pumpkin pie spice, and salt; boil for one minute.

Preheat your waffle maker and grease it lightly.

Pour batter onto hot waffle iron, close the lid, and cook until golden brown and crispy.

Transfer cooked waffles to a plate and keep warm in a low oven.

Serve warm topped with chopped pecans and drizzle with brown butter maple syrup.