Preheat oven to 375°F (190°C).
Cook ground beef: In a large skillet, heat olive oil over medium heat. Add the ground beef and chopped onion, cooking until browned. Drain excess fat.
Add sauce: Stir in marinara sauce, Italian seasoning, garlic powder, salt, and pepper. Let the mixture simmer for 5 minutes.
Layer the lasagna: In a 9x13-inch baking dish, spread a thin layer of sauce on the bottom. Place 4 lasagna noodles over the sauce, followed by 1/3 of the meat sauce, a layer of ricotta cheese, mozzarella cheese, and Parmesan cheese. Repeat the layers twice, ending with a layer of sauce and cheeses on top.
Bake: Cover with aluminum foil and bake for 30 minutes. Then, remove the foil and bake for an additional 10 minutes, until bubbly and golden brown.
Rest before serving: Let the lasagna cool for 5-10 minutes before slicing and serving.