Brown the ground beef in a large skillet; drain excess fat. Add chopped onion and minced garlic, cooking until softened.

Stir in crushed tomatoes, tomato paste, Italian seasoning, salt, and pepper. Bring to a simmer and cook for 15-20 minutes, allowing the flavors to meld.

In a mixing bowl, combine ricotta cheese, egg, and grated Parmesan cheese. Mix well until smooth.

Spread a thin layer of meat sauce in a 9x13 inch baking dish. Arrange a layer of lasagna noodles over the sauce, then spread half of the ricotta mixture, followed by a layer of mozzarella cheese. Repeat layers, ending with meat sauce and mozzarella cheese.

Cover the baking dish with foil and bake at 375°F (190°C) for 25 minutes. Remove foil and bake for another 15 minutes, or until bubbly and the cheese is golden brown.

Let the lasagna rest for 10-15 minutes before slicing and serving. Garnish with fresh parsley if desired.