1. In a large skillet over medium heat, heat the oil. Add the onion, mushrooms, basil and fennel. Saute 4 minutes or until onion is tender.
2. Stir in frozen vegetables. Place fish over vegetables, sprinkle with salt and pepper. Arrange tomato slices over fish. Reduce heat to low, cover and cook for 12-16 minutes or until fish flakes with a fork. Remove from heat, sprinkle with parmesan cheese, cover and let stand about 3 minutes or until cheese is melted.