Heat oven to 325°F. Spray 12x8-inch (2-quart) baking dish with nonstick cooking spray. Cook ziti to desired doneness as directed on package. Drain.
Meanwhile, in large skillet, cook ground beef and onion over medium-high heat for 8 to 10 minutes or until ground beef is thoroughly cooked and onion is tender, stirring occasionally. Add tomatoes, tomato sauce, salt and cinnamon; mix well. Bring to a boil. Reduce heat to medium; cook 10 minutes or until mixture is thickened and thoroughly heated.
Meanwhile, melt margarine in medium saucepan over medium heat. Stir in flour; cook until mixture is smooth and bubbly. Gradually add half-and-half, stirring constantly until mixture boils and thickens. Remove from heat.
Beat egg in medium bowl. Slowly add about half of flour mixture, stirring constantly. Return egg and flour mixture to saucepan. Add 1/2 cup of the cheese; stir to blend well.
Add cooked ziti to beef mixture in skillet; mix well. Layer half of ziti mixture in sprayed baking dish. Sprinkle with 1/2 cup of the cheese. Top with remaining ziti mixture. Spoon white sauce over ziti mixture. Sprinkle with remaining 1/2 cup cheese.
Bake at 325°F. for 25 to 30 minutes or until bubbly around edges, center is set and cheese is browned. Sprinkle lightly with nutmeg. Let stand 10 minutes before serving. To serve, cut into squares.