Put the shallot in a bowl.
Rinse the tarragon and chop 5 leaves.
Add the 5 tarragon leaves, black pepper and vinegar to the shallot.
Microwave for 3 minutes on HIGH until the liquid is reduced to 2 (1) tablespoon.
Filter and return to the bowl.
Set aside.
Rinse the fish and pat dry on kitchen paper.
Season with salt and pepper on both sides.
Put the fillets in a round dish, skin side outward.
Cover and microwave on HIGH for 5-6 minutes according to the thickness of the fillets.
Remove the skin and place the fish on a serving dish.
Cover with aluminum (aluminium) foil to keep it warm.
Cut the butter into tiny pieces and put in a large bowl.
Melt in the microwave oven fori minute on HIGH.
Beatwithahand beater.
Mix the egg yolks and the reduced vinegar liquid together, whisking constantly.
Gradually pour over the butter, stirring gently.
Microwave on MEDIUM for 1 minute.
Whisk again.
If the sauce is smooth and creamy, add the tomato concentrate; if not, microwave for a further 30 seconds on MEDIUM.
Add the tomato concentrate (puree).
Chop the remaining tarragon.
Add to the sauce, pour into a sauceboat