Cut squash in half lengthwise. Remove seeds and membranes. Place cut side down in baking dish with a little water. Cover with Saran wrap, and microwave 10 minutes.
Turn cut side up. Place one half of the butter and 1 teaspoon brown sugar in each cavity. Cover with Saran wrap, and microwave 2 minutes.
Variation: For spaghetti squash, cook the same as above. Scoop out the cooked center. Top with spaghetti sauce and Parmesan cheese.