Cook the lasagna noodles according to the package instructions until al dente. Drain and lay flat on a clean kitchen towel.

In a large skillet over medium heat, cook the ground beef until browned and fully cooked. Season with salt, pepper, and oregano. Drain excess fat.

Stir in the marinara sauce with cooked meat and let simmer for about 5 minutes.

In a mixing bowl, blend the ricotta cheese with the egg.

In a baking dish (9x13 inches), spread a thin layer of meat sauce at the bottom, layer three noodles, followed by a portion of the ricotta mixture, mozzarella cheese, and more meat sauce. Repeat until ingredients are used up, finishing with mozzarella and a sprinkle of Parmesan.

Cover the dish with foil (sprayed with cooking spray) and bake at 375°F for 25 minutes. Remove foil and bake for an additional 15 minutes or until bubbly and golden brown.

Let the lasagna rest for at least 10 minutes before serving.