To preheat grill turn all burners on high, close the lid, and heat until very hot, about 15 minutes. Scrape the grate clean with a grill brush. Leave all burners on high.
Sprinkle both sides of the steak generously with salt and pepper. Grill the steak until well seared and dark brown on one side, 5-7 minutes with lid closed. Using tongs, flip the steak and grill until the interior of the meat when cut is slightly less done than you want it to be when you eat, 2-5 minutes more for rare or medium rare (depending on thickness of steak and heat of fire).
Transfer steak to a cutting board and cover loosely with foil to rest for 5 minutes.
While the steak is resting combine parsley, garlic, chile, olive oil, vinegar, salt, and pepper to taste in a small bowl (sauce can be made up to 3 days ahead of time and stored in the fridge).
Once rested, slice the steak thinly against the grain. Serve immediately with parsley sauce.