Cook the spaghetti in plenty of boiling salted water for about 8 minutes until al dente. Cut tomatoes into quarters, remove seeds as desired. Finely dice the flesh. Pluck sage leaves from the stems and cut into thin strips. Crush garlic finely. Heat olive oil in a large pan. Sauté garlic in it, add strips of sage and let the fat in it foam up.
Fold in the tomatoes and braise briefly. In the meantime, drain spaghetti well in a sieve and toss in sage butter. Season with salt and pepper. Serve in portions. Slice or grate the Parmesan cheese finely and pour over the spaghetti. Serve garnished with fresh herbs as desired