1. Preheat oven to 425 degrees F. Pierce sweet potatoes and bake until tender (1 hour).
2. Combine beans, tomatoes, oil, cumin, coriander, and salt in a small saucepan. Heat through.
3. Slash each sweet potato lengthwise, press open to make a well in the center, and spoon the bean mixture into the well. Top each with a dollop of sour cream and a sprinkle of cilantro.