Preheat the oven to 375°F (190°C).

Cook lasagna noodles according to the package. Drain and lay flat on a tray to prevent sticking.

Heat a large skillet over medium-high heat. Add the ground beef and chopped onion. Cook until the beef is browned and the onion is translucent, about 6–8 minutes. Drain excess fat if needed.

Add minced garlic and cook for 30 seconds until fragrant.

Pour in the marinara sauce. Stir in Italian seasoning, chopped parsley, and salt and pepper to taste. Lower the heat and simmer for 10–15 minutes to meld flavors.

In a medium bowl, combine ricotta cheese and the egg. Season with a pinch of salt and pepper and mix until smooth.

Spread a thin layer of meat sauce across the bottom of a 9x13-inch baking dish.

Place a layer of noodles over the sauce. Spoon and spread a third of the meat sauce over the noodles. Dollop and spread half of the ricotta mixture. Sprinkle with about a third of the mozzarella and a little parmesan.

Repeat layers: noodles, sauce, remaining ricotta, more mozzarella and parmesan. Finish with a final layer of noodles, the remaining sauce, and the remaining mozzarella and parmesan on top.

Cover the dish tightly with foil (tent it slightly so cheese doesn’t stick).

Bake covered for 35–40 minutes. Remove foil and bake an additional 10–15 minutes until cheese is bubbly and golden.

Let the lasagna rest for 10–15 minutes before slicing. This helps it set and makes clean slices.