Step 1: Prepare the Meat Sauce

1. In a large skillet, heat the olive oil over medium heat.
2. Add the chopped onion and sauté until translucent, about 5 minutes. Stir in the minced garlic and cook for an additional 1 minute.
3. Add the ground beef (or pork) to the skillet, breaking it apart with a spoon. Cook until browned and no longer pink, about 7–10 minutes. Drain excess fat if necessary.
4. Stir in the crushed tomatoes, tomato paste, oregano, basil, salt, and pepper. Let the sauce simmer for about 15–20 minutes.

Step 2: Prepare the Cheese Mixture

1. In a bowl, combine the ricotta cheese, egg, grated Parmesan cheese, parsley, salt, and pepper. Mix until smooth.

Step 3: Cook the Noodles

1. In a large pot of boiling salted water, cook the lasagna noodles according to package instructions until al dente. Drain and rinse under cold water to prevent sticking.

Step 4: Assemble the Lasagna

1. In a 9×13-inch baking dish, spread a thin layer of meat sauce on the bottom.
2. Place a layer of noodles over the sauce, followed by a layer of the ricotta mixture, a layer of meat sauce, and a layer of mozzarella cheese.
3. Repeat the layers until all ingredients are used, finishing with a layer of meat sauce topped with mozzarella and extra Parmesan cheese.

Step 5: Bake the Lasagna

1. Preheat your oven to 375°F (190°C).
2. Cover the dish with aluminum foil and bake for 25 minutes.
3. Remove the foil and bake for an additional 15–20 minutes, or until the top is golden and bubbly.
4. Let the lasagna cool for about 10–15 minutes before slicing to allow it to set.