Preheat the oven to 200°C/180°C fan.
Place each half of the fish on a layer of tin foil. Rub each half with garlic and dot with half the butter. Sprinkle over the seafood rub.
Layer both sides with the onions and peppers and tomatoes. Dot over the remaining butter and scatter with dill. Season with salt and pepper, if you wish.
Wrap both halves tightly in tinfoil. Place them in the oven and cook for 30 minutes or until pressed in the thickest part of the salmon it begins to flake. The salmon should still be pink inside.
Place onto a serving plate and serve on the table still wrapped in the tin foil.