Fill a large pot with salted water and bring it to a rolling boil. Add the lasagna noodles and cook them as directed on the package until tender. Drain and set aside to cool slightly.
Heat olive oil in a spacious skillet over medium heat. Add ground beef, stirring frequently, and cook until no longer pink, breaking it into small bits. Drain any fat from the pan.
Stir in the marinara sauce, diced tomatoes, and Italian seasoning into the meat. Let the mixture simmer gently for around 10 minutes. Season with salt and pepper according to taste.
In a separate bowl, blend ricotta cheese, the egg, and 1/4 cup of Parmesan cheese until smooth and creamy. Set this mixture aside.
Preheat your oven to 375°F (190°C). Spread a thin layer of the meat sauce in the bottom of a 9x13-inch dish. Layer 3 noodles over the sauce, followed by half of the ricotta mixture, one-third of the mozzarella, then more meat sauce. Repeat this layering process.
Finish the top with a final noodle layer, cover with the remaining meat sauce, and sprinkle the remaining mozzarella and Parmesan cheeses evenly on top.
Cover the dish tightly with aluminum foil and bake for 25 minutes. Remove the foil and continue baking uncovered for another 20 minutes, or until the cheese on top is golden and bubbling.
Allow the lasagna to rest for 10 minutes before slicing. Garnish with fresh basil or parsley if desired and serve warm.
