Onions peel, in strips cut. Clean, wash and slice the zucchini. Peel and slice the carrots. Clean the fennel, wash some green and put aside. Wash the fennel, cut in half and cut out the hard stalk. Cut the fennel crosswise into strips
Heat 2 tablespoons of oil in a frying pan. Fry the prepared vegetables for 6-7 minutes while turning, season with salt and pepper and remove. Wash the fish, dab dry. Heat 1 tablespoon of oil in the vegetable fat. Fry fish for 7-8 minutes, season with salt and pepper, remove and keep warm. Wash lemon hot, grate dry, grate peel. Halve the lemon, squeeze 1 half. Deglaze the vegetables with cream, stock and lemon juice, bring to the boil and thicken with sauce thickener. Season sauce with salt, pepper, sugar and possibly lemon juice
Add the vegetables, place the fish on top and heat covered. Chop the fennel greens and sprinkle over the pan to serve. If necessary, cut the remaining lemon into slices and serve with it