In a blender or food processor, combine the onion, bell pepper, garlic, parsley, and Italian seasoning. Pulse until finely chopped.
In a large bowl, combine the ground beef, vegetable mixture, breadcrumbs, eggs, Parmesan cheese, salt, and pepper. Mix gently until combined. If the mixture feels too wet, add a little more breadcrumbs.
Shape the mixture into 16-20 meatballs.
Heat the olive oil in a large deep skillet or sauté pan over medium heat.
Brown the meatballs on all sides, working in batches if necessary. Transfer to a plate.
Add the beef broth, tomato sauce, tomato paste, Italian seasoning, and penne pasta to the skillet. Stir to combine.
Return the meatballs to the skillet and bring the mixture to a gentle boil.
Cover, reduce heat to low, and simmer for 12-15 minutes, stirring once or twice, until the pasta is tender and the meatballs are cooked through.
Remove from heat and let rest for 2-3 minutes.
Garnish with fresh parsley and grated Parmesan cheese.
Serve immediately and enjoy.