Saute beef and 1 onion in bacon grease until brown, sprinkling with flour and chili powder during cooking.
Add water to cover and simmer for 30 minutes.
Combine tomato soup, milk, cheese, remaining onion, and season with salt.
Cover the bottom of a greased, 2-quart casserole with a layer of tortillas, then a layer of meat, and top with cheese mixture.
Repeat until all ingredients are used, ending with cheese mixture.
Bake at 325° for about 40 minutes or until cheese has melted and browned.
The meat mixture may be made the day