Scrub the sweet potato clean and use a fork to pierce it 5-7 times on different areas of the skin.
Put the sweet potato on a microwave-safe plate and cook for 2.5 minutes on high. Flip it over and put it back in the microwave for another 2.5 minutes on high. Check to see if it's soft to the touch. If not, put it back in the microwave for 30-second intervals until tender.
Slice the cooked sweet potato in half and top with butter and sea salt.
You can make up to 2 sweet potatoes at a time, but it will likely take closer to 7 minutes total. Microwave in shorter intervals so that you can check the progress along the way, and be sure to flip the sweet potatoes over at the halfway point.
Store cooked sweet potatoes in an airtight container in the fridge for up to 5 days. Reheat in the microwave (of course)!