Preheat oven to 375°F (190°C).

In a large skillet, heat olive oil over medium heat. Add chopped onion and minced garlic; cook until translucent, about 5 minutes.

Add ground beef to the skillet, season with oregano, salt, and pepper, and cook until browned, about 8 minutes.

Stir in marinara sauce and simmer for 10 minutes.

Cook lasagna noodles according to package instructions until al dente. Drain and set aside.

In a baking dish, spread a layer of meat sauce, then layer noodles, ricotta cheese, and shredded mozzarella. Repeat layers ending with mozzarella and parmesan cheese on top.

Bake in the preheated oven for 45 minutes until bubbly and golden brown.

Let sit for 10 minutes before serving.