Brazilian Black Beans and Quinoa

While KC was in college, every Sunday she would go to this great Brazilian restaurant and order an Iron Vegetarian which was a sort of black bean stew served over rice. This recipe was inspired by that dish. Serve with Brazilian Fries (thick wedges of fried potatoes served with mayonnaise, salt, and pepper)

1 c vegetable broth
1 tsp cumin seeds, crushed
1 t ground thyme
2 medium sweet potatoes, peeled, sliced lengthwise into quarters and then into 1/4-inch thick slices
2 medium leeks (white parts only), rinsed well and sliced into 1/2-inch thick slices
1 red bell pepper, seeded and sliced lengthwise into 1/2-inch wide slices
1 medium yellow onion, peeled and sliced lengthwise into 1/2-inch thick slices
2 Tbs. fresh-squeezed lime juice
1 15-oz can fire roasted tomatoes
2 16-oz cans black beans
Plain nonfat yogurt
Cooked quinoa

Heat the broth and add cumin and thyme. Lower the heat to a simmer and cook 1 minute. Add sweet potatoes. Cover and cook 10 minutes. Next add leeks and cook 5 more minutes. Stir in bell peppers and onion. Continue cooking for 5 minutes. Then add lime juice, combine well and cook 5 minutes more. Add tomatoes and beans. Cover and simmer an additional 10 minutes or until sweet potatoes are tender.