In Mexico, Carne Asada literally means "roasted meat" and typically refers to various cuts of beef that has been marinated and grilled. For my version I've marinated skirt steak in lime juice, garlic, cilantro and spices before grilling to a medium rare and slicing thinly against the grain.
Combine all the marinade ingredients in a large Ziploc bag. Kiwi has a powerful enzyme called actinidin that breaks down protein, making it a great addition to the marinade if you don't plan on letting the meat marinate overnight. Taste it and add more salt or sugar if needed. It should be relatively salty, but not so salty that it burns your tongue. The sugar is a personal preference thing. If you like it sweeter, add more sugar. Add the meat to the bag, squeeze out as much air as you can and seal the bag. Let this marinate for at least 1 hour, or preferably overnight in the refrigerator.
When you're ready to grill the meat, remove it from the refrigerator about 30 minutes before cooking to allow it to come to room temperature. This helps ensure the Carne Asada will cook evenly. If you're using a broiler, move the rack to the top position and turn the broiler on high, with a grilling rack on top of a baking sheet. Scrape any excess marinade off the meat and place the meat on the grill. Cook until nicely browned on one side, flip and brown the other side. Skirt steak will cook much faster than hanger steak, so be careful not to overcook it.
Transfer the Carne Asada to a cutting board and let it rest for at least 5 minutes. Use a sharp knife to roughly chop up the meat then add it to a bowl with the sweet onions, cilantro, and any juices that accumulated on the baking sheet or cutting board.
Serve the Carne Asade with fresh tortillas and Pico De Gallo.