1. Combined jalapeño, garlic, cilantro, lime juice, lime zest, olive oil, salt, pepper, and cumin into a large resealable bag or bowl. Add steak and toss to coat. Marinate in the fridge for at least 30 minutes, up to 12 hours.
2. Preheat grill to medium-high heat.
3. In a large bowl, combine all salsa ingredients.
4. Remove steak from marinade; discard leftover marinade.
5. Grill steak three to four minutes per side until it reaches an internal temperature of 145ºF.
6. Let steak rest three to four minutes before slicing thinly against the grain.
7. Warm tortillas on the grill. Divide steak among tortillas and top with mango salsa. Enjoy!