Make the meatballs: In a large bowl, combine the ground beef or sausage, breadcrumbs, Parmesan, egg, garlic, Italian seasoning, salt, and pepper. Mix until just combined. Roll into small meatballs, about 1 inch in diameter.

Brown the meatballs: Heat olive oil in a large soup pot over medium-high heat. Add the meatballs in batches and cook for 4–5 minutes, turning occasionally, until browned on the outside. They don’t need to be completely cooked through yet. Remove and set aside.

Cook the vegetables: Add the onion, carrots, and celery to the same pot. Cook for 5–7 minutes, until softened. Add the garlic and cook for another minute.

Add the broth: Pour in the chicken broth and add the Italian seasoning, salt, and pepper. Bring to a gentle boil.

Cook the meatballs: Carefully return the meatballs to the pot. Reduce the heat and simmer for 10 minutes.

Add the pasta: Stir in the pasta and cook according to the package directions, usually 6–10 minutes, until tender.

Add the spinach: Stir in the spinach and cook for 2–3 minutes, until wilted.

Finish the soup: Stir in the Parmesan cheese and lemon juice. Taste and adjust the salt and pepper as needed.

Serve: Ladle into bowls and top with extra Parmesan cheese. Serve with warm crusty bread.