- Preheat the oven to 375°F (190°C). 
- Cook the lasagna noodles according to package instructions. Drain and set aside. 
- Prepare the meat sauce: In a large skillet, heat olive oil over medium heat. Add the chopped onion and garlic, cooking until softened (about 3 minutes). Add the ground beef and cook until browned, breaking it up with a wooden spoon. Add the crushed tomatoes, tomato paste, oregano, basil, salt, and pepper. Let it simmer for 30 minutes, stirring occasionally. 
- Mix the ricotta cheese: In a bowl, combine ricotta cheese, egg, half of the Parmesan cheese, and fresh parsley. Stir until smooth and set aside. 
- Assemble the lasagna: In a 9x13-inch baking dish, start with a thin layer of meat sauce, then add a layer of noodles. Spread a portion of the ricotta mixture on top, followed by more meat sauce. Sprinkle with mozzarella and Parmesan. Repeat layers until all ingredients are used. 
- Bake: Cover the lasagna with aluminum foil and bake for 30 minutes. Remove the foil and bake for an additional 15 minutes, or until the cheese is bubbly and golden. 
- Rest the lasagna: Let the lasagna rest for 10-15 minutes before slicing and serving. 
- Garnish with fresh parsley before serving.