Preaheat the oven to 200 C , Finely squeeze the juice from one lemon. Seson the fillets with salt and white pepper.
To make the gremolata crust – mix the mustard, parmesan cheese, breadcrumbs, parsley, dill, garlic. Grease the ovenproof dish with the butter and place the fish fillets. Arrange the tomatoes and zucchini around the fish. Sprinkle with the salt, pepper and dried oregano.
Spoon the gremolata mixture over the fish and press down lightly. Drizzle with knob of butter. Bake for 30 minutes.
Top of fish should be cripsy. It was yummy.