Step 1

Preheat the oven to 375 degrees F (190 degrees C). Spray a baking dish with cooking spray.

Step 2

Combine ground beef, onion, crackers, egg, salt, and pepper in a large bowl and mix until well combined. Shape mixture into 1-inch meatballs and place in the prepared baking dish.

Step 3

Bake in the preheated oven until no longer pink inside, about 30 minutes. An instant-read thermometer inserted into the center should read at least 165 degrees F (74 degrees C).

Step 4

While meatballs are cooking, heat 2 tablespoons olive oil in a large pot over medium heat. Add onion, mushrooms, broccoli, carrots, celery, bell pepper, and garlic. Cook, stirring frequently, until vegetables are soft, about 10 minutes. Add tomato sauce, tomato paste, oregano, salt, and pepper. Reduce heat to medium-low and simmer for 15 minutes.

Step 5

Meanwhile, bring a large pot of lightly salted water to a boil. Add spaghetti and oil and boil, stirring occasionally, until tender yet firm to the bite, about 12 minutes.

Step 6

Add cooked meatballs to the sauce and simmer over medium-low heat for 5 minutes.

Step 7

Serve noodles with meatballs and sauce on top. Sprinkle with Parmesan cheese.