Remove the green from the fennel and keep it, it will later serve as a decoration. Halve the fennel and cut into very thin slices. In the meantime, cook the pasta in salted water according to the instructions on the packet until al dente.
Sear the fennel in a coated pan with a little oil, let it take on a strong color. When the slices are brown enough, reduce the heat, juice the lemon and distribute the juice over the fennel.
Season with salt and pepper. When the fennel is soft but still firm to the bite after 5 - 8 minutes, deglaze with red wine, reduce briefly, then add cream and parmesan. Let the sauce thicken for approx. 2 - 3 minutes.
Put the spaghetti in the pan with a tablespoon of pasta water, mix well. Chop the fennel greens and then distribute them on the plate with the spaghetti.