Wash fish, remove bones. Cut fish into 4 strips. Clean, wash and grate carrots into very fine strips (alternatively cut them). Wash and clean the zucchini and also grate into very fine strips.
Peel the onions, quarter one onion and finely dice the rest of the onion. Boil 750 ml water, bay leaves, quartered onion, lemon juice, peppercorns and salt. Add the fish and let it simmer for about 8 minutes on the lowest setting.
Meanwhile cook the vegetables in boiling salted water for about 5 minutes. Pour onto a sieve and drain. Remove 125 ml fish stock and set aside. Heat oil, fry onion cubes in it until translucent, dust with flour and sweat them on.
Deglaze with fish stock, cream and prosecco. Bring to the boil, season with salt, pepper and sugar. Wash the dill, dab dry and chop except for a few flags for garnishing. Arrange fish on vegetable noodles with sauce.
Sprinkle with dill and pepper. Serve garnished with lemon slices, dill flowers and the dill flags.