Marinate flank steak in pineapple juice for at least 30 minutes.
Pat dry beef, then season with salt and pepper.
Heat pan on medium high heat, then add oil.
Sear flank steak 3-5 minutes on both sides depending on your preferred done-ness.
Allow to rest for 5-10 minutes before slicing beef into thin strips.
Assemble wraps with romaine lettuces, cucumber, tomato, beef, onions, and mint leaves.
Then spoon some of the dressing over beef.