1. Pierce sweet potatoes with fork, and microwave 7 to 10 minutes, or until soft. (Or bake 1 hour in 400°F oven.) Cool sweet potatoes 10 minutes, or until easy to handle, and then halve and coarsely chop (leave skins on).
2. Transfer chopped sweet potatoes to food processor, add remaining ingredients, and pulse until smooth, adding up to 2 Tbs. water, if necessary to achieved desired consistency. Season with salt and pepper, if desired. Serve warm or at room temperature, garnished with lime zest, if using.