In a large saucepan, heat olive oil over medium heat. Add garlic and cook until fragrant.
Add ground beef, salt, and pepper. Cook until beef is browned.
Stir in marinara sauce and let simmer for 10 minutes.
In a mixing bowl, combine ricotta cheese, egg, and half of the Parmesan cheese.
In a baking dish, spread a layer of meat sauce. Top with a layer of lasagna noodles. Spread a layer of the ricotta mixture, then sprinkle with mozzarella cheese. Repeat layers, ending with a layer of meat sauce and remaining mozzarella and Parmesan cheese.
Cover with aluminum foil and bake for 25 minutes. Remove foil and bake for an additional 25 minutes, or until cheese is bubbly and golden.
Let lasagna cool for 10 minutes before serving.
Notes:
For a vegetarian version, substitute ground beef with sautéed vegetables like mushrooms, zucchini, and spinach.