For the Steak:
Blend all the ingredients well and place in a shallow bowl big enough to hold the steak overnight or at least for 4 hours in the fridge.

Turn on your grill to the highest setting- you want it SUPER hot before you place the meat down. Make sure to shake off the excess marinade and put the meat down on the grill on an angle so you get the nice grill marks.

Let it cook for about 4 minutes and without flipping it over yet, slightly rotate the beef to get crisscross marks (thank you PW for this trick). Cook for another 4 minutes on this side. Flip over and do the same.

Flank steak tends to be somewhat thick, but if your piece looks thin to you, you might want to cook it for less time to avoid overcooking. Overcooked flank steak is not pretty, friends. In fact, it’s pretty awful because it gets extremely tough.

After the meat is cooked, remove it from the grill – WITH TONGS! You don’t want to pierce it with a fork because this will make all the juices run out, rendering the meat dry.

You have to let the meat rest for a few minutes before you slice it thinly against the grain.

For the chimichurri:

Thoroughly wash the parsley. In a food processor, grind the parsley well and set aside in a large bowl or Tupperware.

Next add the onions and garlic to the food processor. Combine until it becomes a fine paste. Strain this over a tight mesh sieve to remove the excess water from the onion and add to the bowl with the parsley.

Next, add the juice of the lemon and limes, the salt, oil, vinegar and sugar and combine well.

Allow to set overnight or at least four hours. Serve over juicy steak.