1. Preheat your oven to 375°F (190°C). Grease a 9×13 inch baking dish lightly with olive oil.
2. In a large skillet over medium heat, cook the ground beef until browned, about 6-8 minutes. Drain excess fat.
3. Add the chopped onion and minced garlic to the skillet. Sauté for 3-4 minutes until the onions are translucent.
4. Stir in the crushed tomatoes, tomato paste, oregano, basil, salt, and pepper. Let it simmer for 15 minutes, stirring occasionally.
5. In a separate pot, cook the lasagna noodles according to package instructions. Drain and set aside.
6. In a bowl, combine the ricotta cheese and egg, mixing until smooth.
7. To assemble, spread a thin layer of meat sauce on the bottom of your prepared baking dish. Place a layer of noodles over the sauce, followed by half of the ricotta mixture, a third of the mozzarella, and a sprinkle of Parmesan.
8. Repeat the layers: sauce, noodles, ricotta mixture, mozzarella, and Parmesan. Finish with a final layer of noodles, sauce, and the remaining mozzarella and Parmesan.
9. Cover the dish with aluminum foil and bake in the preheated oven for 25 minutes. Remove the foil and bake for an additional 15 minutes, or until the cheese is bubbly and golden brown.
10. Let the lasagna cool for 10 minutes before slicing. Garnish with fresh basil leaves if desired.

Remember, patience is key to achieving the perfect slice. Letting the lasagna rest after baking allows it to set, making it easier to serve.