Season fish with salt and pepper. Rub a 9-inch (or similar sized) baking dish with 1 tablespoon of the butter and arrange fish in dish. In a saucepan, melt remaining butter over medium heat. Stir in cream and bring to a boil. Stir in cheese, Italian seasoning, onions and garlic. Pour sauce over fish and place dish in a preheated 400 degree oven. Cook until top is lightly browned, about 18-20 minutes. Top with tomato before serving.