In a mixing bowl, combine orange juice, lime juice, soy sauce, olive oil, minced garlic, cumin, oregano, black pepper, and salt to create the marinade.

Place the flank steak in a resealable bag or shallow dish and pour the marinade over it. Seal or cover and refrigerate for at least 1 hour, preferably overnight.

Preheat the grill to high heat.

Remove the steak from the marinade and let excess marinade drip off.

Grill the steak for about 5 minutes on each side for medium-rare, or until desired doneness.

Let the steak rest for 5 minutes before slicing against the grain.

Serve the sliced carne asada on warm corn tortillas topped with cilantro, onion, salsa, and avocado.