1. Preheat the oven to 375°F (190°C).

2. Cook the lasagna noodles according to package instructions, then drain and set aside.

3. In a skillet, cook ground beef with onions and garlic until browned. Add marinara sauce and simmer for 10 minutes.

4. In a baking dish, spread a layer of meat sauce, followed by a layer of noodles and a layer of ricotta cheese. Repeat layers until all ingredients are used up, ending with a layer of mozzarella cheese on top.

5. Cover the baking dish with foil and bake for 30 minutes. Remove foil and bake for an additional 10 minutes until the cheese is bubbly and golden brown.

6. Let it cool for 10 minutes before serving.