Sauté Vegetables: In a large soup pot, heat avocado oil or butter over medium heat. Add chopped onion and sauté until translucent, about 5 minutes, stirring occasionally. Add Spices: Add ground cumin, paprika, salt, pepper, and garlic powder to pot. Stir, then sauté until fragrant, about 30 seconds.
Add Sweet Potatoes and Bell Peppers: Add chopped sweet potatoes and red bell peppers to pot. Stir to combine with onion and spices.
Pour in Broth: Add broth to the pot (if you'll be using a blender instead of an immersion blender to blend the soup after cooking, see note below). Increase stovetop heat to high and bring mixture to a boil (this may take 10-15 minutes).
Simmer: Reduce stovetop heat to low and simmer soup uncovered until sweet potatoes are tender, about 20-25 minutes.
Blend Soup: Use an immersion blender to puree the soup directly in the pot until smooth. Alternatively, carefully ladle soup into a blender or food processor, and, in batches, blend until just smooth (do not over-blend), and then return to the pot (you may need to do this in batches, depending on the capacity of your blender).
Add Heavy Cream (Optional): If you want a creamier soup, pour in heavy cream, then stir.
Add Additional Seasoning: Carefully taste soup and, based on preferences, add more salt and pepper.
Garnish and Serve: Ladle soup into bowls and garnish with a dollop of sour cream or yogurt and chopped parsley, then serve.