Preheat your oven to 375°F (190°C) and set the rack to the center position.

In a large skillet over medium heat, add the ground beef and diced onions; cook for 5–7 minutes until browned and translucent, then add minced garlic and sauté for another minute before removing from heat and draining excess fat.

In a saucepan, melt the butter, whisk in the flour for 1–2 minutes, then gradually add milk while whisking to prevent lumps; cook until thickened, then stir in Italian seasoning and half of the Parmesan, adjusting with salt and pepper.

In a mixing bowl, combine ricotta cheese with salt and pepper until smooth.

Spread a thin layer of béchamel sauce in a 9x13-inch baking dish, layer noodles over it, followed by half of the beef mixture, dollops of ricotta, mozzarella, and more sauce; repeat layers, finishing with sauce topped with remaining mozzarella and Parmesan.

Cover with aluminum foil and bake for 25 minutes, then remove the foil and bake for another 15 minutes until golden and bubbly.

Let the lasagna rest for about 10 minutes before slicing.

Slice the lasagna into squares and optionally garnish with chopped parsley before serving.