Crumble beef and onion in two 9 inch pie plates. Brown in 425 oven, stirring occasionally. Meanwhile cook spaghetti and drain. Spread spaghetti over meat mixture. Pour 1 ½ cups of tomato sauce and seasonings over top. Toss lightly. Cover with cheese and choice of pizza toppings. Pour on remaining sauce. Bake @ 350 for 10 minutes.