Cook macaroni in boiling unsalted water until tender; drain. Combine the first egg, the corned beef, onion, mustard and 1/4 cup tomato sauce; mix well. Press into bottom and up the sides of a 9-inch pie plate, forming a shell. Set aside. Combine macaroni, cheese, the remaining tomato sauce and second egg. Turn into the meat shell. Toss the bread crumbs with butter. Sprinkle atop macaroni mixture. Bake in 350° oven for 25 to 30 minutes.