- Cook the tagliatelle for about 2 minutes less than the time indicated on the package. Drain, return to the pan and toss with a small drizzle of olive oil. Set aside.
- Finely chop the garlic, cut the red onion into wedges and slice the cavolo nero into thin strips.
- Heat a little olive oil in a large frying pan or wok. Gently sauté the garlic and onion until softened. Add the cavolo nero and cherry tomatoes and stir-fry for about 5 minutes, until the cavolo nero begins to wilt.
- Pat the entrecôte steaks dry and season generously with salt and pepper. Heat a little oil in a separate frying pan and sear the steaks over high heat for around 2 minutes on each side for medium-rare.
- Add the butter during the final minute of cooking and spoon the melted butter over the steaks. For medium steak, reduce the heat and cook for approximately 2 minutes longer. Remove from the pan, loosely wrap in aluminium foil and leave to rest.
- Pour the white wine into the pan with the vegetables and allow it to reduce slightly. Add the crème fraîche and stir until you have a smooth, creamy sauce.
- Add the tagliatelle and gently toss everything together. Let the pasta simmer in the sauce for another 2 to 3 minutes.
- Divide the creamy tagliatelle between the plates. Slice the rested entrecôte into strips and arrange on top of the pasta.
Serve immediately and enjoy.