Bring a large pot of salted water to a boil and add the lasagna noodles, cooking according to package instructions until al dente, approximately 8-10 minutes. Once cooked, drain the noodles and toss them with 1 tablespoon of olive oil to prevent sticking. Set them aside as you prepare the meat sauce.

In a large skillet, heat 1 tablespoon of olive oil over medium heat. Add the finely chopped onion and minced garlic, sautéing until fragrant and translucent, about 3-4 minutes. Then, add the ground beef, breaking it up with a spatula, and cook until browned, around 5-7 minutes. Stir in the tomato sauce, paste, salt, and half of the chopped parsley, simmering for 20 minutes until the sauce thickens and flavors meld beautifully.

In a mixing bowl, combine the ricotta cheese, half of the shredded mozzarella, grated Parmesan cheese, beaten egg, and the remaining parsley. Mix until well blended and creamy.

In a 9x13-inch casserole dish, start layering your ingredients. Begin with a layer of noodles at the bottom, followed by a generous portion of meat sauce, then a layer of the ricotta cheese mixture. Repeat until all ingredients are used, finishing with a final layer of meat sauce and sprinkling the remaining mozzarella cheese on top.

Preheat your oven to 375°F (190°C). Cover the assembled lasagna with aluminum foil, ensuring it doesn't touch the cheese. Bake in the preheated oven for 60-75 minutes. Remove the foil during the last 15 minutes to allow the cheese to brown.

Once baked, remove the lasagna from the oven and let it rest for 15-20 minutes to allow the layers to set for easier slicing. Serve warm.