Blend onions, green bell pepper, habanero pepper, and oil in a blender until creamy.
Transfer the onion mixture to a stock pot. Add water, peanut butter, bouillon cubes, and salt to the onion mixture. Place a cover on the stock pot and bring the mixture to a boil; cook at a boil for 30 minutes.
Stir the spinach into the boiling mixture; replace the cover on the stock pot and cook until the water has evaporated a bit and the sauce has the consistency of gravy, about 30 minutes more.