Heat the oil in a large pot or Dutch oven over medium heat. Add the onion and cook until soft but not brown, about 10 minutes. Add the garlic and chili and cook for about 5 minutes to soften. Add the tomatoes, stir to combine then add the Sunbutter, stirring it in until smooth. Add the water and salt, stir, then add the sweet potatoes. Cover the pan and simmer until the sweet potatoes are tender but not falling apart, about 15 minutes.
Add the black beans, corn, spinach and arugula and cook until the beans and corn are heated through and the spinach and arugula is wilted. Serve with or without rice.