Brown ground beef with onion (and garlic if preferred). Cook until ground beef is no longer pink, drain. Add taco seasoning and 1/4 cup water. Let simmer 5 minutes. Drain tomatoes and add to ground beef. Spray a 2-Quart casserole dish with cooking spray. Layer: tortilla, beef mixture, and cheese. Repeat layers until all tortillas, beef and cheese are used, ending with cheese. Cover and bake for 20 minutes at 375 F. Top with lettuce (and sour cream if desired).
