Fry the onion and garlic in a pan to the point of transparency.
Blend peeled tomatoes (after boiling them first) and add them to the pot along with the basil leaves. In another separate pot boil the pasta for 12 minutes or until al dente.
Add the Parmesan cheese to the sauce and simmer until just before serving.
Drain the pasta and rinse in cold water to stop cooking.
To serve, pour the sauce over the pasta and garnish with basil leaves.