1. In a small bowl, cover the sundried tomatoes with the boiling water and set aside.
2. In a soup pot, saute the onions, garlic, and chile or cayenne in the oil for about 5 minutes, stiring frequently, until the onions are translucent.
3. Add the cumin, 1/3 cup water, and the juice from the tomatoes. Break up the tomatoes by squeezing them into the soup pot, or chop them coarsley right in the can. Cover and bring to a boil.
4. Lower the heat and simmer, covered, for 5 minutes. Add the black beans and their liquid and continue to simmer, stirring occasionaly to prevent sticking.
5. Drain and chop the softened sun-dried tomoatoes. Add them to the soup and cook for 5 to 10 minutes longer until the onions are tender. Stir in the cilantro and remove the soup from the heat.
6. Puree half of the soup in a blender or food processor and return it to the pot. If the soup is too thick, add some water or tomatoe juice. Reheat gently.
Serve each bowl with a dollop of yogurt or sour cream