Preheat the waffle maker: Preheat your waffle iron according to the manufacturer's instructions. Lightly grease the plates with cooking spray if needed.
Combine the dry ingredients: In a large mixing bowl, whisk together the flour, baking powder, baking soda, salt, pumpkin pie spice, and cinnamon.
Mix the wet ingredients: In a separate bowl, whisk together the pumpkin purée, milk, eggs, melted butter, brown sugar, and vanilla extract until smooth.
Make the batter: Gradually add the dry ingredients to the wet ingredients. Stir gently with a spatula until just combined. Do not overmix; a few small lumps are fine.
Add batter to the waffle maker: Spoon the appropriate amount of batter into the center of the preheated waffle iron. Close the lid and cook according to your waffle maker's instructions.
Cook until golden brown: Cook until the waffles are golden brown, crisp around the edges, and cooked through. Avoid opening the waffle maker too early.
Remove and serve: Carefully remove the waffles and place them on a wire rack. Serve warm with maple syrup, whipped cream, butter, toasted pecans, or your favorite toppings.
Keep extra waffles crisp: If making a larger batch, place finished waffles on a wire rack instead of stacking them. This prevents trapped steam from making them soft.