Preheat your oven to 375°F (190°C).
In a large skillet, brown the ground beef over medium heat. Drain any excess fat.
Add the chopped onion and minced garlic to the skillet. Cook until the onion is translucent.
Stir in the crushed tomatoes, oregano, salt, and pepper. Simmer for 15 minutes.
Meanwhile, cook the lasagna noodles according to package instructions until al dente. Drain and rinse with cold water.
In a bowl, mix ricotta cheese, egg, and a pinch of salt until well combined.
Spread a thin layer of meat sauce on the bottom of a 9x13 inch baking dish.
Layer three lasagna noodles over the sauce, followed by half of the ricotta mixture, one-third of the mozzarella, and one-third of the meat sauce.
Repeat the layering process—noodles, ricotta, mozzarella, and sauce—until all ingredients are used, finishing with a layer of noodles topped with the remaining sauce and mozzarella.
Sprinkle grated Parmesan on top and cover the baking dish with aluminum foil.
Bake in the preheated oven for 25 minutes. Remove the foil and bake for an additional 15 minutes, or until the top is bubbly and golden.
Let the lasagna cool for at least 15 minutes before slicing and serving.
