Peel the shallot. Blanch (scald) the tomatoes with boiling water, peel, remove the stalk and core the tomatoes. Cut the flesh into cubes. Rinse the fresh chervil, rub dry and chop coarsely. Squeeze the lemon.
Cut the vanilla beans in half lengthwise and scrape out the pulp with a small kitchen knife. Bring to a boil in the frying pan together with vermouth, vinegar and a piece of shallot pressed through a garlic press and cook at high temperature. Pour fish stock and reduce sauce. Add 25 g of butter, chervil and diced tomatoes and season strongly with salt and freshly ground pepper. Stir the ice-cold butter into the sauce, which is no longer boiling. Keep the sauce warm.
Rinse the fish fillets, acidify with the juice of one lemon, season lightly with salt and season with pepper. Heat clarified butter and roast the fillets on the skin side until crispy, turn to the other side and quickly finish cooking. Serve the fish with the vanilla butter on plates.
Tip: Instead of clarified butter, you can also use butter in most cases.