Heat oven to 200 degrees F and a waffle iron to medium-high heat. Lightly oil the top and bottom of the waffle iron or coat with nonstick spray.In a large bowl, combine flour, sugar, baking powder, baking soda, pumpkin pie spice, cinnamon, and salt.In a medium bowl, whisk together buttermilk, pumpkin puree, eggs, and butter. Pour mixture over dry ingredients and stir just until moist but slightly lumpy.Pour 1/3 cup of the pumpkin mixture into the waffle iron, close gently, and cook until golden brown and crisp, about 4-5 minutes; keep warm in the oven.Serve immediately.