In a large bowl, whisk together lime juice, orange juice, minced garlic, cumin, chili powder, chopped cilantro, olive oil, salt, and pepper to create the marinade.

Place flank steak in a large zip-top bag or shallow dish and pour marinade over the meat. Seal and refrigerate for at least 2 hours, or up to 24 hours for best flavor.

Remove steak from refrigerator 30 minutes before cooking to bring to room temperature. Preheat grill or grill pan to medium-high heat.

Remove steak from marinade and discard excess marinade. Grill steak for 5-6 minutes per side for medium-rare, or until it reaches your desired doneness.

Transfer steak to a cutting board and let rest for 5 minutes. Slice thinly against the grain at a slight diagonal.

Warm tortillas on the grill or in a dry skillet for 30 seconds per side until soft and pliable.

Serve sliced carne asada in warm tortillas topped with diced onion, fresh cilantro, and lime wedges on the side.