Preheat oven to 500 degrees F.
Begin by preparing the vegetable base for the fish. Heat 1/3 cup of olive oil in a large saucepan over medium heat. Add the eggplant, season with salt and pepper and cook for 10 minutes until just tender. Set aside on a platter. Add the zucchini to the pan and cook in the same way until just tender and remove to the platter with the eggplant. Add to the pan, smashed anchovies, onion, garlic and fennel. Cook for 5 to 7 minutes until caramelized then add tomatoes and tomato paste and cook for a further 5 minutes until wilted. Season with salt and pepper and add the red pepper flakes. Combine all the vegetables together in a large roasting pan.
Now prepare the fish. Get your fishmonger to prepare the tail piece of your fish so it is cleaned and boned, and ready to go when you get home. Begin by vertically scoring the fish in 4 places, skin side up so the cuts pierce the skin and reveal the flesh. Prepare the basil compound butter by chopping half of the basil and mixing it with the room temperature butter until well combined. Season with salt and pepper.
Season the piece of fish with salt and pepper and smear the top of the fish with basil butter then take the whole fish and transfer to the roasting tray and place on top of the bed of vegetables.
Sprinkle the buttered fish with the bread crumb mixture.
Place in hot oven and roast for 12 to 15 minutes for medium rare, then finish under the broiler for 2 minutes to crisp the skin. Do not over cook, otherwise the fish will be dry.
To serve, portion the fish along the score marks, serve with a scoop of the vegetables.
Put bread, herbs, garlic and 1/3 cup of olive oil in a food processor and pulse until you have the texture of coarse bread crumbs. They should be a vibrant green from the olive oil and the herbs. Season well with salt and pepper and toast over medium heat in a large saute pan until crispy.