Prepare beans; keep warm. Stack tortillas, wrap in foil, and heat in 350 oven for 15 min.
Meanwhile, place lettuce, tomato, bell pepper & onions in a large salad bowl. Then prepare dressing; combine vinegar, garlic, chili powder, cumin, salt, and pepper; add oil and blend well.
To serve, toss salad with dressing. To assemble a taco, spoon 1/4 cup salad, 1 tsp cheese, and 1/3 tbsp yogurt.
Black Beans
Sort 1 cup dried black beans to remove any debris. Rinse and drain beans. In a 3 qt saucepan, bring 4 cups water to a boil. Add beans; boil for 2 minutes. remove from heat, cover, and let stand for 1 hour. Drain and rinse beans.
Heat 1 tbsp olive oil in a 3 qt pan over med heat. Add 1 large onion, chopped; cook stirring occasionally, until soft (about 10 min). Add beans, 1 clove garlic (minced), 1 small dried hot red chile (crushed), 1/2 tsp salt, and 21/2 cups water. Bring to a boil over high heat. Reduce heat, cover and simmer until liquid is absorbed and beans are very tender (about 2 hours).