Cook the tagliatelle in plenty of salted water until cooked.
Finely chop the onions and garlic and sauté in a little butter. Add the thawed spinach leaves and sweat well. Season with salt and pepper. Stir the sour cream into the spinach, season with lemon pepper. Cut the smoked salmon into strips and fold into the spinach and sour cream mixture. Strain, fold in and serve the finished cooked ribbon noodles.