Combine onion, oil, 3 garlic cloves, and tomatoes in a bowl; toss to coat vegetables. Arrange tomato mixture on a foil-lined baking sheet. Broil 10 minutes or until vegetables char slightly, stirring after 5 minutes. Spoon tomato mixture into the bowl of a food processor; pulse 6 times or until mixture is coarsely chopped. Combine tomato mixture, marinara, and 3/8 teaspoon salt in a medium saucepan; bring to a simmer.
Mince remaining 3 garlic cloves. Combine minced garlic, remaining 1/8 teaspoon salt, panko, red pepper, beef, and egg in a large bowl; mix gently just until combined. Working quickly with damp hands, gently shape beef mixture into 12 meatballs (do not pack). Arrange meatballs in a single layer on a baking sheet coated with cooking spray. Broil 6 inches from heat for 6 minutes, turning meatballs once. Remove pan from oven. Add meatballs to tomato mixture; simmer 4 minutes or until meatballs are done.
Cook pasta according to package directions, omitting salt and fat. Serve meatballs and sauce over pasta; sprinkle with cheese.
MyRecipes is working with Let's Move!, the Partnership for a Healthier America, and USDA's MyPlate to give anyone looking for healthier options access to a trove of recipes that will help them create healthy, tasty plates. For more information about creating a healthy plate, visit www.choosemyplate.gov.