Cook the pasta in abundant salted water. When "al dente", do no drain it - simply transfer the pasta to a large bowl using tongs or a spaghetti spoon and reserve cooking liquid.
Add 2 ladles of the cooking liquid and about 3/4 of the grated Pecorino cheese. Toss well but gently so you do not break the spaghetti. Sprinkle 1 tablespoon of freshly grated black pepper over the pasta. If the pasta is too dry, add some more cooking water; if it is too runny, add some more cheese.
Portion onto 4 plates; serve right away extra grated Pecorino cheese.