Fire up the grill or oven to 450F – 500F. Once hot, add the peeled tomatillo directly on the grill grates to char. If using the oven, place them in a baking tray, spray with oil, add a pinch of salt on them, then roast for 12 – 15 minutes, or until the outside has blistered some and tomatillos are soft to touch. Set aside to cool down.
Mix together the ingredients for the marinade.
Place the flank steak in a sealable bag or a baking tray and add the marinade. Close/Cover and marinate for at least 30 minutes at room temperature, or overnight in the fridge.
Add the tomatillos and remaining ingredients for the dressing to a high powered blender or food processor. Process until smooth and season to taste with sea salt & pepper. Set in the fridge to chill.
Increase the heat of the grill to 550F – 595F. If using the oven, set it to broil and make sure the rack is in the middle.
Shake off excess marinade and other pieces of food that may stick to it and gently pat it dry with a paper towel. Place the flank directly on the grill, or place it in a baking tray. Cook for 4 – 6 minutes on 1 side, then flip to the other side to cook for an additional 3 – 5 minutes, depending on your desired level of doneness. Add an additional 1.5 – 2 minutes per side for a medium well steak.
Remove the steak and let it rest for at least 10 minutes. Lightly cover with foil as it cools down.
OPTIONAL – If desired, spray each Romaine heart half with oil on the cut portion, then place it on the grill to sear for 3 – 5 minutes.
Slice the flank steak and bring it all together!
Drizzle dressing over the Romaine heart, then add the steak and garnish with more parsley, pepper and pepitas for some crunch!