1: Prepare the Meat Sauce

1. Heat olive oil in a large skillet over medium heat. Add the chopped onion and sauté until soft and translucent, about 3-4 minutes.
2. Add minced garlic and cook for 1 minute until fragrant.
3. Add the ground beef or turkey to the skillet. Cook until browned, breaking up the meat into small pieces with a spoon. Drain any excess fat.
4. Stir in the crushed tomatoes, tomato paste, oregano, basil, sugar, salt, and pepper. Reduce heat to low and let the sauce simmer for 30 minutes, stirring occasionally to blend the flavors.

2: Make the Béchamel Sauce

1. Melt butter in a medium saucepan over medium heat. Once melted, whisk in the flour to form a smooth paste (roux). Cook for 1-2 minutes, stirring constantly.
2. Gradually add the warm milk to the roux, whisking continuously to avoid lumps. Cook for 5-7 minutes until the sauce thickens.
3. Season with nutmeg, salt, and pepper. Remove from heat and set aside.

3: Assemble the Lasagna

1. Preheat your oven to 375°F (190°C). Grease a 9×13-inch baking dish lightly with oil or butter.
2. Spread a thin layer of meat sauce on the bottom of the baking dish. Lay 3-4 Barilla oven-ready lasagne sheets on top, ensuring they do not overlap.
3. Add a layer of meat sauce, then drizzle with béchamel sauce. Sprinkle mozzarella and ricotta cheese evenly over the top.
4. Repeat the layers: lasagne sheets, meat sauce, béchamel, and cheeses, until all the ingredients are used. Finish with a generous topping of shredded mozzarella and grated Parmesan.

4: Bake the Lasagna

1. Cover the baking dish with aluminum foil to prevent the top from drying out. Bake in the preheated oven for 25-30 minutes.
2. Remove the foil and bake for another 15-20 minutes, or until the cheese on top is golden and bubbly.
3. Let the lasagna rest for 10 minutes before slicing and serving.