Steam onion and sweet potato in soup pot with ½ cup of the water for about 5 minutes. Add beans, tomatoes, barley, remaining water, cumin, salt, and chili powder. Bring to a boil, then reduce to a simmer for 20-30 minutes, until barley and sweet potato are cooked. Add cilantro and lime juice. Heat through, test flavor and adjust if necessary, and serve. Top with additional fresh chopped cilantro if desired. Serves 4-6.
