1. Preheat oven to 350 degrees F. Place squash halves face down in casserole pan filled with 1/2" water. Place in oven for about 10-15 minutes.
2. Mix brown sugar with apples. Take the squash out of the oven, place face up, and fill the cavities with the apple mixture.
3. Add a pat of margarine to each and top with a shake or two of nutmeg and salt, if using.
4. Cover very lightly with foil, and bake until the apples and the squash are soft and cooked, approximately another 1/2 hour.