I went to the butcher and he swears flank steak is better for tacos?!
Answers:
Taquerías in Mexico offer a selection of beef. The prefered being "costilla" which is from down at the end of the ribeye muscle I think and something called "arrachera" which is usually marinaded and looks like a filet that has been cut wrong. Some of my friends are certain that this arrachera is what is called skirt steak in the USA. Arrachera has become popular because it is more tender than the usual taquería beef and doesn't need to have the dickens beat out of it to tenderize like most Mexican meat.
The correct way to make beef tacos is to first grill the meat and then chop it into small bits. I have cooked flank steak myself. I suggest you cook it first and then with a very very sharp knife slice it as tghin as possible across the grain of the steak. It can be very tasty but unless you cut it just right it's hard to chew. Also slice that tendon off!
In my opnion the very best meat for beef tacos is #1 filete #2 ribeye # 3 Tbone
I live and eat tacos in Mexico
Everyone where I live uses skirt steak because it is cheaper, but you use the steak that you like for yourself. Who cares what other people use. The Guatemalans in WA use skirt steak and it seems to be oiler than other cuts, it is stringy and chewy, but they cut it on the diagonal across the grain. Like I say and like Justin Wilson the Cajun chef used to say. Eat or drink what you like. Use a steak that you would eat on your plate with A-1 on it. Use what you like.
Lots of eating.
Skirt steak can be a great cut, very tender. Try getting veal skirt steak. If there are tendons, or white skin, then cut that off. Flank steak is good, you might want to marinate it with some vinegar and taco spices; cumin, cinnamon, cocoa, cayenne pepper, ect. let marinate for a half hour. Cook it in the oven till it is medium. Cut against the grain. If you pull the meat apart and you see lines where it kind of separates, you don't cut down or along these lines. You cut across as if to make a t with the grain and the knife. I am pretty sure that skirt steak cost more then flank steak. It is definitely more tender, thats why I suggest marinating the flank.
Maybe he said that because flank costs more than skirt (hence, more $$$ for him)?....
Either cut should be sliced against the grain (not at an angle like london broil - as Alton Brown said in his fajita (sp?) show, you don't see it so it doesn't have to look pretty). That same show, he recommended skirt over flank.