In a large pot over medium heat, saute the onions in ¼ cup broth or water until they are soft and translucent. Add more liquid if the pan gets too dry. Add the garlic, ginger, cinnamon, nutmeg, salt, and black pepper. Let it cook for a few minutes to toast the spices.
Add the diced sweet potato, red lentils, pumpkin puree, 1 cup water, and 4 cups broth to the pot. Increase the heat and bring it to a simmer and then reduce the heat to medium. Cover with the lid and let it cook for 25 minutes or until the sweet potatoes and lentils are soft.
Take the pot off the heat and let it cool for 10 minutes. Carefully, transfer the mixture to a large blender cup. Only fill it ⅓ of the way full. (Do not blend hot, bubbling, or boiling soup.)
Remove the small center feeder cap from the blender lid and secure the lid on top of the cup. Fold a thick dish towel into a square and cover the feeder cap opening to catch any splatters.
Hold the towel down with your hand and blend on low in small batches until it's smooth and creamy. Transfer the pureed soup to a large bowl and then repeat this step until you've blended everything in the pot.
Pour all of the soup back into the pot, stir in the coconut milk, and let it warm up. Add more salt and pepper to taste.
Optional - Garnish with roasted pumpkin seeds, chives, and a drizzle of coconut milk before serving. (Drag a knife or toothpick through the coconut drizzle to make a swirl pattern like the pictures).
Notes
If your blender cup doesn't have any kind of vent in the lid for the heat/steam to escape through, let the soup cool completely before blending it.
Make sure to use pureed pumpkin, not pumpkin pie filling. They are not the same!
Peel the sweet potatoes before dicing them. After blending, if the skin is left on you will see little flakes in the soup.
Store leftovers in an airtight container in the fridge for 3 days or you can freeze it for 2-3 months.