Make Buttermilk: In a large bowl, whisk the apple cider vinegar and milk until well combined. Set aside for 5 minutes to slightly thicken and curdle.
Combine Dry Ingredients: In a medium bowl, whisk the flour, pumpkin pie spice, baking powder, baking soda, salt, and, sugar in a small bowl until well combined.
Combine Wet Ingredients: To the large bowl with the buttermilk, add the pumpkin puree, oil, and vanilla then whisk well until combined.
Combine Wet and Dry: Add half of the dry ingredients and fold together with a spatula. Add the remaining dry ingredients and fold until just combined. Don’t overmix. The batter will be thick and small lumps are fine.
Preheat the waffle iron according to the manufacturer’s instructions. If your waffle iron is not non-stick, lightly spray it with nonstick cooking spray otherwise leave it bare. (*Optional: To keep waffles warm after cooking, preheat the oven to 200°F)
Cook Waffles: Spoon the amount of batter recommended by the manufacturer onto the hot waffle iron (typically, ⅓ cup per waffle. I used a heaped amount of batter in a 2-ounce ice cream scoop which is about ⅓ cup). Cook according to the manufacturer’s instructions until the waffle is golden brown. Let the steam dissipate completely before opening the waffle maker. Serve: Serve immediately or set them on a cooling rack to allow air to circulate or place them in the preheated oven. Do not stack or overlap them. Top with fresh fruit, vegan butter, maple syrup, coconut whipped cream, nuts, or pumpkin seeds.