Gouge and scale the fish. You should let the fishmonger do that for you. Wash the fish again and pat dry thoroughly.
Spread half of the butter on a flat, ovenproof dish. Scald the tomatoes, peel, core and cut into small cubes. Peel and finely chop the garlic. Spread the tomatoes, garlic, bay leaves and thyme in the pan. Put the fish on it. Brush with the olive oil. Cut the lemon into slices and top the fish with it. Pour white wine.
Fry in a preheated oven at 180 - 200 ° C for approx. 25 minutes.
Puree the meat stock with the vegetables (remove the bay leaves beforehand) and whip up with the rest of the butter. Fold in 1 tablespoon chopped herbs (basil, tarragon, or parsley) and season with salt and pepper.