1. Mix ground beef, onion and garlic in 2-quart casserole. Microwave on high (100%) until beef loses pink color, 5 - 9 minutes, stirring once to break up beef. Drain.
2. Stir in tomato sauce, water, chili powder, salt and pepper. Microwave on high (100%) until sauce is slightly thickened, 6-10 minutes stirring after half the cooking time. If not using a carousel microwave, rotate after once or twice during cooking.
3. Alternately layer tortillas, meat sauce and cheese in 1-1/2 quart round casserole, ending with layer of cheese. Microwave on high (100%) until cheese is melted and bubbly, 1 to 3 minutes. Let stand 2 to 3 minutes.