HEAT oven to 375ºF.
SPOON 1/2 cup rice onto center of each of 2 large sheets of heavy-duty foil with sides slightly turned up. Pour 1/2 cup warm water over each mound of rice; top with 1 fish piece. Arrange spinach around fish; drizzle with dressing.
BRING up foil sides. Double fold top and ends to seal each packet, leaving room for heat circulation inside. Place in single layer in shallow pan.
BAKE 15 min. Cut slits in foil to release steam before opening packets; top with cheese.