In a large soup pot, heat ¼ vegetable broth. Add onion and cook until softened about 5-7 minutes adding more vegetable broth if needed to keep from sticking.
Add the chili powder, cayenne (if using), salt, pepper, sweet potatoes, cauliflower, and garbanzo beans. Stir and cover with vegetable broth adding more broth if necessary.
Bring mixture to boil and reduce heat to a simmer. Partially cover and cook until sweet potatoes are tender about 25-30 minutes. Taste for seasonings.
Garnish with some chopped red Fresno chili if you like a little heat. This is also delicious over brown rice or quinoa.