Add pasta, broth, milk or cream, tomatoes, garlic, onion, salt, and pepper to a large pot.

Bring to a boil; then reduce to a steady simmer.

Cook 10–12 minutes, stirring more often than you think you should—this keeps the pasta from sticking and helps the sauce thicken.

When most of the liquid is absorbed, turn off the heat.

Stir in the basil and Parmesan.

Let it rest for 5–10 minutes so the sauce settles and becomes silky.