Lasagna is the most famous and savory of all Italian baked dishes. Today it is made all over Italy, but this rich and complex dish originated in the region of Emilia-Romagna, specifically Bologna. The key to this dish is seasoning each layer with salt and pepper as you put together the dish.

For the Besciamella Sauce: Place the butter into a medium saucepan and place on the stove over a medium heat to melt. Once melted, whisk in the flour until smooth and continue to cook until the flour turns a light golden color, about 2 minutes.

Meanwhile, heat the milk in a medium saucepan over medium-high heat until simmering. Slowly pour the milk into the butter-flour mixture, whisking constantly to prevent lumps. Simmer, stirring often with a wooden spoon, until the mixture has thickened, about 15 minutes. Season with the salt and set aside.

For the Lasagna: Preheat an oven to 450°F and position rack in the center. Grease a 9-inch by 13-inch baking dish with butter and set aside.

Heat a large pot of water over high heat until boiling. Add enough kosher salt to season the water to taste like sea water. While salted water boils vigorously, add one sheet of the pasta at a time and cook until it floats to the surface, 10 to 15 seconds. Carefully remove with a slotted spoon and plunge into a large bowl of ice water to stop further cooking. Remove from the water when cool. Lay pasta sheets out, being careful not to let them touch, on clean, damp kitchen towels and cover with more damp towels.

Line the bottom of a prepared baking dish with a layer of pasta, trimming the sheets with a knife so that they fit in one even layer (patch if necessary). Spread evenly with 1½ cups of the Bolognese sauce, sprinkle lightly with some of the cheese and season with salt and pepper. Add another layer of pasta, evenly spread 1½ cups of Besciamella sauce on the pasta then sprinkle lightly with cheese, season with salt and pepper. Repeat layers (you will have 3 layers of Bolognese sauce and 2 of Besciamella), ending with Bolognese sauce and Parmigiano. Reserve any extra Bolognese for another use.

Transfer the lasagna to the oven and bake for 10 minutes. Increase the oven temperature to 500°F and cook until the lasagna is bubbling around the edges and browned on the top, about 5 to 7 minutes more. Do not overcook.

Allow the lasagna to rest for 10 minutes before serving.