Wash and dry the sweet potato; do not peel it. Pierce the skin several times with a fork to allow steam to escape.
Place the sweet potato on a microwave-safe plate. Microwave on high for 3 minutes, then flip it over and microwave for an additional 2-3 minutes, or until it becomes tender.
Let the sweet potato rest for 2 minutes. Cut it open and spread the butter inside. Season with salt and pepper to taste. Serve immediately.