It’s thinly sliced sirloin of beef. It’s pre-marinated in a blend of citrus juice (I believe lemon, never paid that much attention to the ingredients), pepper, onions and garlic and probably some other spices. It’s THE best carne asada i’ve ever had and i’ve tried everything from regular grocery store variety to ethnic meat market and this doesn’t even compare to any of those!!! My recommendations on cooking is to grill it on a bbq at around 350-400 degrees, flipping the meat over about every 3-5, total cooking time being roughly 15 minutes.