Place each fillet on a double thickness of heavy-duty foil (about 12 in. square). Top with mushrooms, tomato, garlic, basil, salt and pepper. Fold foil around salmon and seal tightly. Place on a baking sheet.
Bake at 400° for 15-20 minutes or until fish flakes easily with a fork. Open foil carefully; sprinkle with cheese. Bake, uncovered, 5 minutes longer or until cheese is melted.