Cover bottom and sides of 13 x 9 x 2 inch baking dish with 10-12 corn tortillas. Pour beef mixture over tortillas. Place another layer of tortillas over meat mixture. Pour cheese mixture over 2nd layer of tortillas. Bake at 350° for 30 minutes. Sprinkle diagonal rows over casserole of cheese, lettuce, tomatoes, green onions, and black olive.