Preheat your oven to 400°F (200°C).

In a large mixing bowl, combine the ground beef, breadcrumbs, chopped onion, minced garlic, egg, grated Parmesan cheese, chopped parsley, salt, and pepper. Mix gently.

Roll the mixture into balls about 1 to 1.5 inches in diameter and place them on a lined baking sheet.

Bake for 20-25 minutes, turning halfway through, until browned and the internal temperature reaches 160°F (71°C).

In a saucepan, heat olive oil over medium heat, add crushed tomatoes and Italian seasoning, and let simmer for 10-12 minutes.

Toss the baked meatballs in the sauce and let them soak for about 5 minutes before serving.