First, grab a medium-sized bowl and combine all the wet ingredients. Whisk together the buttermilk, pumpkin puree, light brown sugar, vegetable oil, egg, and vanilla extract until they are well blended. A smooth consistency here ensures the flavors are evenly distributed from the start.
Next, add the dry ingredients directly into the bowl with the wet mixture. Sprinkle in the all-purpose flour, pumpkin pie spice, baking powder, salt, and baking soda. Whisk everything together just until combined. Be careful not to over-mix; a few small lumps are perfectly fine.
Once mixed, cover the bowl with plastic wrap and place it in the refrigerator. Let the batter chill for at least two hours, or even overnight. This resting period is crucial; it helps the gluten relax and the spices infuse, resulting in more tender and flavorful waffles.
While the batter chills, prepare the syrup. Add the unsalted butter to a small skillet over medium heat. Cook, swirling the pan occasionally, until the butter turns a golden brown and gives off a nutty aroma, which should take about 4 to 5 minutes.
Once the butter is browned, carefully add the maple syrup, pumpkin pie spice, and salt to the skillet. Bring the mixture to a boil for one minute. Remove it from the heat and stir in the vanilla extract. This syrup is the perfect finishing touch.
Preheat your waffle iron according to its instructions. Once hot, spray it with nonstick cooking spray. Pour the chilled batter onto the iron, close the lid, and cook until the waffles are golden brown and crispy. Repeat this process with the remaining batter.