Preheat the waffle iron. Set it to medium-high heat so the batter hits a hot surface and crisps quickly.
Lightly oil or spray the plates.
Whisk your dry ingredients. In a large bowl, combine gluten-free flour, cornstarch, baking powder, baking soda, salt, pumpkin pie spice, and brown sugar. Break up any brown sugar clumps with your fingers.
Mix the wet ingredients. In a separate bowl, whisk pumpkin purée, buttermilk, eggs, vanilla, and melted butter or oil until smooth.
Bring it together gently. Pour the wet mixture into the dry and whisk until just combined. A few small lumps are fine.
If adding chocolate chips or nuts, fold them in now.
Rest the batter briefly. Let it sit for 5 minutes. This lets the flour hydrate and helps the waffles rise evenly.
Cook the waffles. Scoop batter onto the hot iron (usually about 1/2 to 3/4 cup depending on your iron). Close and cook until deeply golden and crisp, typically 4–6 minutes.
Avoid peeking too early.
Hold them crisp. Place finished waffles on a wire rack set over a baking sheet in a 200°F (95°C) oven to keep them crisp while you cook the rest.
Serve your way. Top with maple syrup, a dollop of yogurt or whipped cream, and a sprinkle of cinnamon. Fresh berries or sliced pears are great with pumpkin spice.