Preheat your oven to 375°F (190°C).

In a large pot, bring salted water to a boil. Cook the lasagna noodles according to package instructions until al dente. Drain and set aside.

In a skillet, heat a drizzle of olive oil over medium heat. Add chopped onions and minced garlic, cook until softened. Add the ground beef and cook until browned. Drain excess fat if necessary. Stir in crushed tomatoes, tomato paste, basil, oregano, salt, and pepper. Simmer the sauce for about 10-15 minutes, stirring occasionally.

In a mixing bowl, combine ricotta cheese and egg until well mixed.

Spread a thin layer of meat sauce on the bottom of the baking dish. Place 3 lasagna noodles on top. Spread half of the ricotta mixture over the noodles, followed by a third of the shredded mozzarella cheese and a third of the Parmesan cheese. Repeat this layering process - meat sauce, noodles, ricotta mixture, mozzarella, and Parmesan cheese. Top with a final layer of meat sauce and remaining shredded mozzarella and Parmesan cheese.

Cover the baking dish with aluminum foil, making sure it's tightly sealed around the edges to prevent drying. 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.

Let the lasagna cool for a few minutes before slicing. Garnish with chopped fresh parsley if desired. Serve hot and enjoy your delicious homemade lasagna!