Preheat the oven to 375°F (190°C).
In a large saucepan, heat the olive oil over medium heat. Add the chopped onion and minced garlic, cooking until the onion is soft, about 5 minutes.
Add the ground beef to the pan and cook until browned, breaking it apart with a spoon (about 8-10 minutes). Drain any excess fat.
Stir in the marinara sauce, salt, and pepper. Allow the mixture to heat through for about 5 minutes, then remove from heat.
In a separate mixing bowl, combine the ricotta cheese, egg, fresh basil, and a pinch of salt and pepper. Mix until thoroughly combined.
Spread a thin layer of meat sauce on the bottom of the sheet pan. Place 3 sheets of lasagna noodles on top of the sauce (they can overlap slightly).
Spread half of the ricotta mixture over the noodles, followed by a third of the mozzarella cheese.
Repeat this layering process: add another layer of meat sauce, 3 more sheets of lasagna noodles, the remaining ricotta mixture, and another third of the mozzarella.
Place the last 3 sheets of lasagna noodles on top, followed by the remaining meat sauce.
Finish with the remaining mozzarella cheese and sprinkle the grated Parmesan over the top.
Cover the sheet pan with aluminum foil and bake for 25 minutes.
Remove the foil and bake for an additional 20 minutes, or until the cheese is bubbly and golden.
Allow the lasagna to cool for about 10 minutes before cutting into squares and serving.