Prick sweet potatoes with a fork in several places. Microwave on High until tender all the way to the center, 12 to 15 minutes. (Alternatively, place in a baking dish and bake at 425 degrees F until tender all the way to the center, about 1 hour.)
Meanwhile, in a medium microwaveable bowl, combine beans, tomatoes, oil, cumin, coriander and salt; microwave on High until just heated through, 2 to 3 minutes. (Alternatively, heat in a small saucepan over medium heat.)
When just cool enough to handle, 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.
