Sorry, I am a day late posting this fabulous recipe from Alton Brown tweaked a little by me.
2tsp Lime Zest
1/4 cup Lime Juice
1/2 cup Vegetable Oil
1/3 cup Dark Soy Sauce
4 Scallions, washed and cut into quarters
2 cloves of minced garlic
1/2 tsp of Red Pepper flakes
1/2 tsp ground Cumin
3 tbls brown sugar
2 lbs of flank steak (you can use skirt as well just don't let it marinate for more than an hour or it will begin to cook from the line juice)
Throw all of the ingredients except for the steak into the blender and puree until combined. Cut the steak into two or three equal portions (for more even cooking) and place in a gallon size zip bag, pour the marinade over the steak and refridgerate for two to three hours turning several times.
Heat your grill to scorching (or 650 degrees) place the steaks on the grill and let cook on each side for two to four minutes depending on thickness, this will be fast beacuse we want to sear all the juices in. Remove steak from the grill and let rest for 5 minutes before slicing thinly across the grain!
Serve with peppers and onions (I roast them in the oven with a little oil, salt, and pepper at 350 for 30 min while the grill heats and the steaks are cooking) cheese, flour tortillas (best if heated) guacamole and sour cream!