Take the flank steak and use a meat tenderizer on it - pound it out a few times all over. Place the flank steak in a baking dish or a Ziplock bag. In a bowl, whisk together the cilantro, olive oil, lime juice, lime zest, garlic, red pepper flakes, salt and pepper. Pour it over the flank steak and marinate anywhere from 30 minutes to 2 hour or even overnight!
When you’re ready to cook the steak, you can grill, broil or pan sear it to your liking. We tend to broil it as we find that the easiest. Preheat the broiler in your oven and move the oven rack as close as possible. Place the steak on a broiler pan or baking sheet and broil on each side for about 5 minutes. This usually results in a medium doneness - but since the edges are thinner, they tend to be more well done.
Allow the steak to rest for 10 minutes before slicing it thinly against the grain. While the steak is resting, toss together the cherry tomatoes, onions and cilantro with a pinch of salt and pepper. Juice half the lime over top and toss well.
Place the tomatoes on top of the sliced flank steak and serve. We love to do this as tacos, on salads, or as a main dish with rice or potatoes, along with a green veggie like asparagus or broccoli.