Peel garlic and dice finely. Wash parsley and shake dry. Pluck the leaves and chop them. Mix approx. 2 tablespoons parsley and approx. 1⁄3 of the garlic. Rinse fish and dab dry. Make several light cuts on both sides.
Spread the parsley mix in the incisions. Season with salt and pepper.
Preheat oven (electric cooker: 200 °C/ circulating air: 175 °C/ gas: see manufacturer). Lightly oil a fat pan (deep baking tray; 32 x 39 cm). Spread fish on top. Wash the tomatoes, spread around the fish and sprinkle with sea salt.
Sprinkle everything with 100 ml oil. Bake in a hot oven for 30-40 minutes.
For the salsa verde capers and anchovies rinse and drain. Blend both with the rest of the parsley and garlic and 75 ml oil with a hand blender. Season to taste with salt and pepper.
For the salad, clean and wash the fennel and peel the onions. Slice both finely. Peel oranges so that the white skin is completely removed. Remove the fillets with a sharp knife between the parting skins, squeeze out the parting skins and collect the juice.
Clean and wash the radicchio and cut into fine strips. Mix vinegar with orange juice, approx. 1⁄3 of garlic, salt, pepper and sugar. Fold in 5 tablespoons of oil. Season to taste again. Mix the prepared salad ingredients with the olives and the vinaigrette.
Serve gilthead with salad and salsa verde.