In a large saucepan, combine the beans, broth, water, cumin, oregano, black pepper, and ground red pepper. Bring to a boil over high heat. Reduce the heat to low, cover, and simmer, stirring once or twice, for 15 minutes, or until the flavors are blended.
Meanwhile, heat the oil in a small nonstick skillet over medium heat. Add the bell peppers and cook, stirring frequently, for 4 minutes, or until tender.
Ladle half of the soup into a food processor or blender. Process or blend until pureed. Return the puree to the pan; add the lemon peel.
Ladle the soup into bowls and top each serving with the bell peppers.