Cut flank steak into strips 1/4-inch wide and 3 inches long and marinate in Worcestershire sauce, liquid smoke, juice of 1 lime and garlic for 20 minutes.
(Note: boneless skinless chicken breasts should be "fileted" in half before cutting into 1/4x3-inch strips).
While meat is marinating, cut onion and bell pepper into 1/4-inch wide strips and heat in non-stick skillet with oil until they begin to sweat (don't let them become too soft).
Remove them to a paper plate to drain.
Drain meat and brown in same skillet until done.
Remove to paper plate to drain.
Wipe out the skillet so it is dry and begin to reheat it over a medium heat.
Take one tortilla and put a small amount of grated cheese, 1/4 of the meat (or amount to suit), onion and bell pepper to suit and cover with another small amount of grated cheese and top with a tortilla.
Carefully put "tortilla sandwich" in the heated dry skillet and cook until cheese melts (about 60-90-120 seconds). Flip and cook on other side same amount of time.
Tortilla will take on a lovely "tanned" appearance and become just slightly crispy.
This dinner sounds involved but is actually quite simple and very quick.
Kids and adults both will love it served with iced tea, pico de gallo, guacamole and salsa.