Mix sea salt with 150-200 ml water. Wash and slice the lemon. Wash herbs and dab dry. Wash fish inside and outside and dab dry. Fill with the lemon slices and herbs.
Preheat oven (electric cooker: 200 °C/circulating air: 180 °C/gas: see manufacturer). Line a baking tray with baking paper. Spread a third of the salt as a base on the baking tray. Place the fish side by side on the salt and cover with the remaining salt.
Cook in the hot oven on the middle shelf for 15-18 minutes. Remove from the oven and leave to rest for about 5 minutes.
Meanwhile wash and finely dice the tomatoes. Chop the olives coarsely. Peel and finely dice the shallot. Peel garlic and chop finely. Wash basil and shake dry. Leaf
Mix the prepared ingredients with olive oil, vinegar and lemon juice. Season with salt, cayenne pepper, pepper and 1 pinch of sugar.
Tap the salt crust all around with a knife, carefully loosen and lift off. Remove the fish fillets from the bone. Serve with the tomato and olive salsa.