Preheat your oven to 375°F (190°C).

Cook the lasagna noodles according to the package instructions until al dente, or skip this step if using no-boil noodles.

In a large skillet over medium heat, add the chopped onion and minced garlic; cook until soft (about 3-4 minutes).

Add the ground beef, break it up with a spatula, and season with salt, pepper, and oregano. Cook until browned, draining excess fat if necessary.

Stir in the marinara sauce and let it simmer for about 5 minutes.

In a separate bowl, mix ricotta cheese, egg, a pinch of salt, and half of the grated Parmesan until well blended.

Spread a thin layer of the meat sauce in the bottom of a deep baking dish. Layer with 4 lasagna noodles.

Spread half of the ricotta mixture over the noodles, sprinkle with mozzarella, and repeat layers: sauce, noodles, ricotta, mozzarella.

Finish with a layer of noodles topped with meat sauce, remaining mozzarella, and Parmesan.

Cover with aluminum foil, ensuring it doesn't touch the cheese.

Bake in the preheated oven for about 25 minutes. Remove the foil and bake an additional 10-15 minutes until cheese is bubbly and golden brown.

Let the lasagna rest for 10 minutes before serving. Garnish with fresh basil if desired.