Boil the cauliflower in salted water over low heat. Meanwhile, wilt the thinly-sliced onion together with the oil in a frying pan.
Add the peeled tomatoes after having removed the core and the seeds and reduce by simmering for five minutes.Add the boiled cauliflower and salt and pepper to taste.
Cook the tortiglioni in plenty of boiling, salted water. Drain the pasta and combine it with the sauce in the frying pan, add a good handful of roughly chopped up basil, pepper and, if desired, a handful of Pecorino cheese.