Prepare the meat sauce: In a large skillet, brown ground beef over medium-high heat. Drain any excess fat. Add the diced onion and garlic and cook until softened. Stir in tomato paste, crushed tomatoes, oregano, basil, salt, and pepper. Simmer for at least 30 minutes, stirring occasionally.
Make the béchamel sauce: In a saucepan, melt butter over medium heat. Whisk in flour and cook for 1-2 minutes to form a roux. Gradually whisk in milk until smooth. Bring to a simmer, stirring constantly, until the sauce thickens. Remove from heat and stir in grated Parmesan cheese, salt, and nutmeg.
Cook the lasagna noodles according to package directions. Drain and rinse with cold water to prevent sticking.
Assemble the lasagna: Preheat oven to 375°F (190°C). Spread a thin layer of meat sauce in the bottom of a 9x13 inch baking dish. Layer with lasagna noodles, meat sauce, béchamel sauce, and mozzarella cheese. Repeat layers until all ingredients are used, ending with a layer of mozzarella cheese.
Bake for 30-45 minutes, or until the cheese is melted and bubbly and the lasagna is heated through.
Let the lasagna rest for at least 10-15 minutes before slicing and serving.
Garnish with fresh basil, if desired, and serve warm.
Really enjoyed this lasagna! It was a crowd-pleaser at my potluck. The meat sauce was delicious. I used a mix of ground beef and Italian sausage for a bit more flavor. The only thing I would change is maybe a bit more seasoning in the sauce.
