Peel and finely chop the onion. Clean, wash and slice the fennel. Wash the fish, dab dry, rub with salt and sprinkle with lemon juice. Heat the oil in a pan and fry the onions and fennel for about 5 minutes, turning them over. Deglaze with wine and braise for another 5 minutes. Mix crème fraîche, salt and pepper. Put the fennel in a casserole dish and place the fish on top.
Pour the crème fraiche over it and place the fat in flakes on top. Bake in a preheated oven (electric: 200 °C / gas: level 3) for approx. 25 minutes. Wash the parsley, dab dry and chop finely, except for a little to garnish. Serve the casserole sprinkled with parsley and coloured pepper. Garnish as desired with lemon slices and parsley. Delicious with baguette