Lower the heat to medium-low and add the onions along with additional oil, if needed. Sauté until tender, about 5-7 minutes.
Add tomatoes and bring to a simmer, stirring occasionally.
Season to taste with basil, salt, red pepper, and black pepper.
Set the "meatballs" in the sauce and stir to coat. Continue to simmer until heated through.
While the sauce is simmering, cook and drain pasta according to package directions.
Divide pasta between heated bowls, top with sauce and meatballs, and additional grated Parmagiano-Reggiano.