Preheat your oven to 375°F (190°C).

In a large pot, bring salted water to a boil and cook the lasagna noodles according to package until al dente, about 8-10 minutes. Drain and rinse under cold water.

In a large skillet over medium heat, brown the ground beef until fully cooked, about 6-8 minutes. Drain excess fat, stir in the marinara sauce, and let it simmer for 5 minutes.

In a mixing bowl, combine the ricotta cheese, egg, oregano, salt, and pepper. Whisk until smooth and creamy, about 2-3 minutes.

In a baking dish, layer meat sauce, noodles, half of the ricotta mixture, and a third of the mozzarella. Repeat layers and finish with remaining meat sauce and mozzarella.

Cover tightly with foil and bake for 25 minutes. Remove foil and bake for another 15-20 minutes until the cheese is bubbly and golden brown.

Let the lasagna sit for 10 minutes before slicing to allow the layers to set.