Step 1: Heat the olive oil in a large skillet over medium heat. Add the finely diced onion and sauté until translucent (3-4 minutes). Add minced garlic and ground beef, cooking until browned (5-7 minutes). Drain excess fat, return to skillet, and add marinara sauce, oregano, salt, black pepper, and sugar. Simmer for 10 minutes.
Step 2: In a large pot, bring salted water to a boil. Cook lasagna noodles according to package instructions until al dente. Drain and set aside.
Step 3: Preheat oven to 375°F (190°C). In a 9x13 inch baking dish, spread a thin layer of meat sauce on the bottom. Layer three noodles over the sauce, followed by half of the remaining meat sauce and ⅔ cup mozzarella cheese. Repeat layering with noodles, sauce, and cheese. Finish with the last three noodles, remaining sauce, and sprinkle with remaining mozzarella and parmesan cheese.
Step 4: Cover lasagna with aluminum foil and bake for 25 minutes. Remove foil and bake for an additional 15-20 minutes until cheese is bubbly and golden brown.
Step 5: Let the lasagna rest for 10-15 minutes before slicing and serving hot.
Notes
For added richness, consider adding a layer of ricotta cheese mixed with an egg and herbs. You can also make a vegetarian version by substituting ground beef with vegetables.