Melt the butter; set aside. In a large bowl, combine the next 8 ingredients. Mix together well. Mix in the flour, baking powder and baking soda. The mixture will be lumpy. In another bowl, beat together the milk, sour cream, eggs, and vanilla. Add the liquid mixture to the pumpkin mixture and stir until combined. Fold in the melted butter.
Heat a waffle iron or griddle for pancakes to 350 degrees F and cook. Serve with pure maple syrup.