I was waiting my turn at the meat counter when the Mexican man in front of me bought some sliced chuck roast for carne asada. Curious, I asked him for the recipe and here's what he told me to do: marinade the meat overnight with Montreal steak seasoning with some "Pappy's" marinade with paprika to give it some color. Add diced onions and squeeze a whole orange in it. Grill, chop and serve with tortilla and onion/cilantro. Does that sound authentically Mexican enough?