1pound penne 

2pounds ground lamb 

2onions, finely chopped 

1can (6 ounces) tomato paste 

½ teaspoon ground cinnamon 

2cups water 

6tablespoons (¾ stick) unsalted butter, cut into pieces 

½ cup all-purpose flour 

3cups milk 

⅛ teaspoon cayenne pepper (optional) 

¼ cup finely grated parmesan cheese

1 Preheat oven to 375°F.Bring a pot of water to a boil; add a generous amount of salt. Cook pasta until al dente according to package instructions; drain.

2 Meanwhile, cook lamb in a large saucepan over medium heat, breaking meat apart with a wooden spoon, until no longer pink, 6 to 8 minutes. Add onions; cook, stirring occasionally, until translucent, about 5 minutes.Transfer lamb mixture to a colander; drain off fat, and discard. 

3 Return lamb mixture to pan; Stir in tomato paste, cinnamon, and the water; simmer, stirring occasionally, until thickened, 15 to 20 minutes. Season with salt and black pepper. 

4 Meanwhile, make béchamel sauce: In a medium saucepan, melt butter over medium heat. Whisk in flour until incorporated; cook, whisking, 1 minute. In a slow, steady stream, whisk in milk until completely smooth.Cook, whisking often, until mixture is bubbling and thick enough to coat the back of a wooden spoon, 6 to 8 minutes. Stir in cayenne, if using, and parmesan. 

5 Add pasta to lamb mixture; transfer to a 9-by-13-inch baking dish. Pour béchamel sauce over the top, smoothing with the back of a spoon until level. 

6 Bake until browned in spots, 35 to 40 minutes. Remove from oven; let cool 15 minutes before serving.