Cook the pasta in boiling salted water according to the instructions on the packet. In the meantime, clean and wash the spring onions and cut them into diagonal rings. Clean, wash, quarter and cut the salad into pieces. Wash lemon hot, grate dry, finely grate peel.
Halve the lemon and squeeze the juice of one half. Peel garlic and chop finely. Slice parmesan. Drain the pasta, collecting 100 ml of pasta water.
Heat the oil in a large frying pan. Briefly fry the radicchio, spring onions and garlic vigorously. Add pasta water, lemon juice and zest. Add pasta and about 1/4 of the cheese and mix, season with salt and pepper.
Arrange on plates, sprinkle with remaining Parmesan cheese.