I made this last night for dinner and everyone–including our finicky baby–liked it.
On a 12″ square of foil, drizzle a little olive oil. Place mahi-mahi fillet (thawed, if frozen) onto the foil and flip so it is coated on both sides with the oil. Sprinkle on some bay seasoning (or other seasoning) and some Parmesan cheese. Close foil over the fish to make a little packet. (I made four fillets, so four packets.) Bake at 350 for 10-20 minutes until fish is completely white and flakes easily with a fork.