Prick the squash in three or four places with the tines of a fork. Place it on a microwave-safe plate, cover loosely with microwave-safe plastic wrap, and cook at full power (650 to 700 watts) for 9 minutes. Turn the squash over, and cook another 9 minutes. Then let it stand, still covered, for 5 minutes.
Using a sharp knife, cut a small X in the bottom of each