Pierce potatoes with a fork and wrap individually in a double thickness of paper towels. Microwave on high for 5 minutes. Rotate the potatoes and microwave on high until tender, about 5 minutes more. Unwrap the potatoes and let cool slightly. Cut off a 1 cm thick slice along the top of each potato. With a melon baller or teaspoon, carefully hollow out the potatoes, leaving the shells. Put the insides in a medium-sized bowl, and mash with a fork or potato masher. Add sour cream, buttermilk, cilantro and salsa; mix well. Season with salt and pepper. Fill the shells with the potato mixture. Arrange the potatoes in a microwave-safe pie plate or baking dish. Cover with vented plastic wrap. Microwave on high for 5 minutes, or until heated through. Sprinkle the potatoes with cheese and serve.