Grilled Skirt Steak with grilled onions and peppers( any other veggier you
like),
all wrapped up in warm tortillas and a salsa de jour to top it with :

Don't care if you call it Arracheras or Fajitas, or even if Booger doesn't
think it "authentico" enough for him, a grilled Skirt is good if done right.
I prefer the inner 121D, or use a flank if you can't get skirt. Low and
slow or fast
and hot (braised or grilled after marinating) is up to you.

http://www.beeffoodservice.com/cuts/Info.aspx?Code=18

http://find.myrecipes.com/recipes/re...e_id=16 22410

General info on Beef cuts and prep:
http://www.beeffoodservice.com/Resource/Training.aspx

An alternative to cebollas encurtidas is cebollitas asadas:
http://www.epicurious.com/recipes/food/views/14150