In a 25 cm skillet, brown beef, sausage and onion; drain fat.
Add tomato paste, water, oregano and salt; simmer 5 minutes.
In a 2.5 quart casserole layer half the macaroni, half the meat sauce and half the cheese. Repeat layers using remaining macaroni, meat sauce and cheese.
Bake at 375 degrees 20 to 25 minutes.