Clean the monkfish and cut into cubes. Fry briefly in a little olive oil until the fish turns white on the outside. Take out of the pan and keep warm.
Finely dice the shallot and garlic and sauté in the pan until translucent. Then add the vermouth. Bring everything to the boil briefly and add the tomatoes to the sauce. Season with salt and pepper. After about 5 minutes stir in the crème fraîche and reduce the heat significantly. Add the fish and let it simmer in the sauce for about 5 minutes. Before serving, add the finely chopped tarragon to the sauce.
The monkfish can be replaced in whole or in part by prawns.