If desired, preheat the oven to 200 degrees to keep the pancakes warm between batches. To a high-powered blender, add the buckwheat flour and pumpkin puree, then pour the milk over the top so that the flour is moistened. Add the remaining ingredients: eggs, oil, maple syrup, vanilla, apple cider vinegar, baking soda, salt, and spices. Blend until combined, stopping to scrape down the blender once or twice as needed. Heat a large skillet or griddle over medium low heat. Low and slow is key to cooking these pancakes to ensure that they cook through but do not burn. Don't rush it! Lightly coat with cooking spray or a small amount of oil. Once the pan is hot, for each pancake, pour 1/4 cup of the batter onto the pan. Let cook until the pancakes look dry at the ends, about 3 minutes (bubbles will not form on top). Flip and cook on the other side until golden, about 90 additional seconds. Serve immediately with any desired toppings or place in the oven to keep warm until ready to serve.