Preheat the oven to 190°C (375°F) and lightly grease a baking dish.
Heat olive oil in a pan and sauté onion until soft, then add garlic and cook briefly.
Add ground beef and cook until browned while breaking it apart.
Stir in tomato sauce, crushed tomatoes, tomato paste, seasoning, salt, pepper, and sugar, then simmer for 15–20 minutes.
In a bowl, mix ricotta cheese, egg, Parmesan, and parsley until smooth and creamy.
Spread a thin layer of meat sauce in the baking dish and place lasagne sheets on top.
Add ricotta mixture, mozzarella cheese, and meat sauce over the pasta sheets.
Repeat layers until ingredients are finished, ending with sauce and mozzarella on top.
Cover with foil and bake for 25 minutes, then uncover and bake another 15–20 minutes until golden and bubbly.
Let the lasagne rest for 10–15 minutes before slicing and serving.