1. Heat a large saucepan over medium-high heat; coat pan with cooking spray. Add onion; sauté 3 to 4 minutes or until tender. Add meatballs, pasta sauce, and pesto to pan; bring to a boil. Reduce heat; simmer 10 minutes or until meatballs are thoroughly heated. Spoon meatballs and sauce over Herbed Spaghetti Squash, and sprinkle with Parmesan cheese, if desired.