In a large nonstick skillet, cook the beef, onion and green pepper over medium heat until meat is no longer pink. Stir in the water, flour, chili powder, garlic powder, cumin, coriander and salt. Bring to a boil. Reduce heat; simmer, uncovered, for 5-6 minutes or until thickened.
In a small bowl, combine beans and salsa. Place two tortillas in a round 2-1/2-qt. baking dish coated with cooking spray. Layer with half of the beef mixture, bean mixture and corn; repeat layers. Top with cheese.
Bake, uncovered, at 350° for 25-30 minutes or until heated through and cheese is melted. Let stand for 5 minutes before cutting. Serve with lettuce and tomatoes if desired. Yield: 6 servings.