Prepare the marinade (if using): Mix together ¼ cup vegetable oil, lime juice, minced garlic, cumin, pepper and salt.
Pour the marinade into a non-reactive glass or stainless steel bowl. Dip each one of the steaks into the marinade, making sure that both sides are coated with marinade mix. Prick each one all over with a fork. Stack the steaks into another non-reactive dish and pour any remaining marinade in over them. Cover the dish and refrigerate for at least 3 hours. Drain steaks right before grilling; discard marinade.
Prepare the onions and cactus: Wash the onions and remove the roots. Leave the green parts whole or trim them, leaving at 5 inches to facilitate moving them onto and off the grill. Rinse and drain the cactus pads. With a sharp knife make three long cuts about ¾ of the way down each one in such a way as to form four “legs” that will fan out a bit but without tearing the pad apart; this will allow the heat to reach the inside of the cactus to cook it.
Grill your food: Heat the grill and place the steaks, cactus pads, and onions directly over the heat. With a brush or a spoon, spread a little vegetable oil over each cactus piece and onion help them cook without burning. Grill the meat and vegetables over moderate heat, turning when needed; remove when cooked and slightly charred to taste. (Cactus pads are cooked when they changed from their original bright green to a dull olive green in color.) As the individual pieces of meat and vegetables finish grilling, place them on a platter and keep warm. Once everything’s cooked, take your platter to the table.
Assemble your tacos: Heat your tortillas and place a piece of meat and a “leg” (strip) or two of cactus into each one. (Pull the steaks apart with your hands or with two forks if they are bigger than what you need.) Serve with the table sauce of your choice and the cut limes for each person to squeeze directly on to the meat as desired. Eat the onions with your hands as a side (also sprinkled with lime and salt, if desired); bite off and consume the bulbous white end, leaving the long green parts on your plate to discard or to save for another use.
Refrigerate any leftovers, then reheat in the microwave when you`re ready to enjoy them again. Leftover cactus is delicious as a vegetable side dish or chopped and stirred into scrambled eggs, soup, or a saucy entree.
Nopal cactus pads (or “paddles”) can be purchased from most Hispanic grocery stores and at some larger mainstream supermarkets. If you can find the ones that have had their thorns removed, they are much more convenient. If not, remove the thorns as follows: Work slowly with a very sharp paring knife in a scraping motion to cut the thorns off the cactus flesh. Don’t “peel” the cactus; rather, just cut away the individual thorns. A little of the cactus “skin” will get cut off with each thorn, and that is fine. Rinse each pad in water after you have cleaned it.
Cambray (or Chambray) onions, also called Mexican spring onions, are the scallions or spring onions that you may already be familiar with, but they’ve been left to grow until a definite round bulb has formed on the white end. Their flavor is a bit milder and sweeter than that of less mature spring onions, making them the perfect choice for eating grilled.
Mexican limes, also called key limes, are the small round limes used in Latin America and the Caribbean. Don´t substitute Persian limes (the larger, oblong ones that look like green lemons), because their flaver is not the same. Read more about Mexican limes.
Rustic Campfire-style Mexican Carne Asada https://comboplate.net/rustic-campfire-style-mexican-carne-asada/