In a large pot, brown the ground beef over medium heat. Drain off any excess grease.

Add the chopped onion and cook until softened, about 5 minutes. Add the minced garlic and cook for 1 minute more until fragrant.

Stir in the crushed tomatoes, tomato paste, water, basil, oregano, salt, and pepper. Bring to a simmer, then reduce heat and cook for at least 20 minutes, stirring occasionally.

In a medium saucepan, melt the butter over medium heat. Whisk in the flour and cook for 1-2 minutes, until lightly golden.

Gradually whisk in the milk until smooth. Bring to a simmer, stirring constantly, until the sauce thickens. Stir in the salt and nutmeg.

Preheat your oven to 375°F (190°C).

Spread a thin layer of meat sauce in the bottom of a 9x13 inch baking dish.

Layer with 3 lasagna noodles, followed by about one-third of the remaining meat sauce, one-third of the béchamel sauce, and one-third of the mozzarella and Parmesan cheeses.

Repeat the layers two more times, ending with the remaining béchamel sauce and cheeses.

Cover the dish with aluminum foil and bake for 25 minutes.

Remove the foil and bake for another 15-20 minutes, or until the cheese is melted and bubbly and the edges are golden brown.

Let the lasagna rest for 10 minutes before slicing and serving.