Heat a liberal amount of butter or margarine in the bottom of a cast iron skillet. Brown one side of a flour tortilla in the butter or margarine. Flip the tortilla over and spread with grated Monterey jack or whichever cheese you prefer. You may also sprinkle sliced jalapeños and/or sliced black olives over the top. Cook just until the cheese melts.
Serve with salsa and/or guacamole.