In a large bowl, whisk together buttermilk, pumpkin puree, yogurt, eggs, coconut oil, maple syrup, and vanilla extract. Add the flour, cornmeal, baking powder, baking soda, cinnamon, nutmeg, allspice, and salt. Fold the dry ingredients in with a wooden spoon or rubber scraper until just moistened. Do not overstir.
Ladle the batter into a waffle iron and bake until brown and crisp on the outside. Repeat with the remaining batter.
Serve waffles with butter, chopped pecans, and pure maple syrup.