Crumble ground beef in a 2 quart glass dish. Microwave on high for 5 minutes, stirring occasionally. Drain excess fat. (I use a plastic colander). Stir into meat mixture the onion, garlic powder, chili powder, cumin, tomato sauce and water. Microwave on 70% power for 5 minutes. In a 2 quart round casserole, alternate layers of 1 tortilla, 1/6 of meat sauce, and 1/6 of cheese, making a torte like casserole. The last layer should be cheese. Cover and microwave at 70% power until torte is bubbly hot and cheese is melted (about 5 mintues).