1Prep the salsa:
In a small bowl, combine pineapple, mango, red onion, lime juice, cilantro (if using), and salt. Stir and set aside.
2Season the steak:
Rub flank steak with olive oil, steak rub, salt, and pepper. Let it sit at room temperature while the grill or pan heats.
3Cook the steak:
Grill or sear the steak over medium-high heat for 3–4 minutes per side, or until cooked to your desired doneness. Let rest 5 minutes before slicing thinly against the grain.
4Warm the tortillas:
Heat tortillas in a dry skillet or directly over a low flame until warm and pliable.
5Assemble the tacos:
Fill each tortilla with sliced steak and a generous spoonful of pineapple mango salsa. Add any extra toppings if you like, and serve immediately.