Preheat oven to 200°C, fan oven 180°C, Gas Mark 6.
Mist a baking sheet or roasting pan with low fat cooking spray, and place the fillets of fish on top. Arrange 1 sliced tomato on top of each fish fillet.
Finely grate the zest from the lemon and set aside. Squeeze the juice from half the lemon and sprinkle over the fish fillets.
Mix together the lemon zest, breadcrumbs, herbs, most of the Parmesan cheese and the olive oil. Season. Share between the fish fillets, spreading it over the tomatoes. Sprinkle the reserved Parmesan cheese on top.
Slice the remaining lemon half and arrange beside the fish fillets.
Transfer to the oven and bake for 12-15 minutes, or until the fish is opaque and flakes easily when tested with a fork. Serve with lightly cooked fresh vegetables
Note: Replace the cod with haddock or halibut fillets if you prefer.