Preheat your oven to 350°F (175°C) and boil a large pot of salted water. Cook lasagna noodles until al dente, about 8-10 minutes. Drain and set aside.

In a large skillet, brown the ground beef and Italian sausage. Add diced onion and minced garlic, cooking until the meat is browned and onion is translucent. Drain excess fat and stir in pasta sauce, tomato paste, Italian seasoning, and black pepper. Simmer for 5 minutes.

In a separate bowl, mix mozzarella, Parmesan, ricotta cheese, parsley, and beaten egg. Season with a pinch of salt and combine until smooth.

In a 9x13-inch baking dish, spread 1 cup of meat sauce, layer with 3 noodles, followed by ⅓ of the cheese mixture. Repeat two more times, ending with noodles topped with remaining meat sauce.

Cover the dish with aluminum foil and bake for 45 minutes.

After 45 minutes, uncover and sprinkle remaining mozzarella and Parmesan on top. Bake uncovered for an additional 15 minutes until cheese is golden-brown.

Remove from oven and let rest for 15 minutes before slicing.