Turn your gas burner to medium-low and using tongs, place tortilla, one at a time, directly over the flame. As soon as it starts to brown, give a quick flip to color the other side and then take off heat. Alternatively, you can cook tortillas in a cast iron skillet - Place tortilla in a hot cast iron skillet, for about 15 to 30 seconds on each side. You want to look few browned or darkened spots on both sides. Keep them warm wrapped in a clean kitchen towel.