Cut squash in half; discard seeds. Place squash cut side down in a microwave-safe dish. Cover and microwave on high for 10-12 minutes or until tender. Turn squash cut side up. Fill centers of squash with brown sugar and butter. Sprinkle with a little salt and pepper. Cover and microwave on high for 2-3 minutes or until heated through.
Acorn Squash in the Microwave