In A Large Nonstick Skillet, Cook Beef And Onion Over Medium Heat Until Meat Is No Longer Pink; Drain. Stir In The Tomatoes, Tomato Sauce, Corn, Water, Chili Powder, Oregano And Salt. Bring To A Boil. Add Macaroni. Reduce Heat; Cover And Simmer For 20-25 Minutes Or Until Macaroni Is Tender. Sprinkle With Cheese; Cover And Cook 2-3 Minutes Longer Or Until Cheese Is Melted.As54