Prepare the meat sauce: In a large pot, brown ground beef over medium-high heat. Drain any excess fat. Add chopped onion and garlic, and cook until softened. Stir in crushed tomatoes, tomato paste, Italian seasoning, salt, and pepper. Bring to a simmer, then reduce heat and cook for at least 30 minutes, stirring occasionally.
Cook the lasagna noodles: Cook lasagna noodles according to package directions. Drain and rinse with cold water to prevent sticking. You can also use oven-ready noodles (no pre-cooking required).
Prepare the ricotta mixture: In a bowl, combine ricotta cheese, egg, grated Parmesan cheese, chopped parsley, salt, and pepper. Mix well.
Assemble the lasagna: Preheat oven to 375°F (190°C). Spread a thin layer of meat sauce in the bottom of a 9x13 inch baking dish. Layer with lasagna noodles, ricotta mixture, and mozzarella cheese. Repeat layers until all ingredients are used, ending with a layer of meat sauce and mozzarella cheese on top.
Bake the lasagna: Cover the baking dish with foil and bake for 25 minutes. Remove the foil and bake for an additional 20 minutes, or until the cheese is melted and bubbly and the lasagna is heated through.
Rest and serve: Let the lasagna rest for 10-15 minutes before cutting and serving. This allows the layers to set and makes it easier to slice.
Garnish with fresh basil leaves, if desired. Serve with a side salad and garlic bread for a complete meal.
