Sprinkle both sides of the steaks with salt.
To make the gremolata, blend the lemon zest, garlic and parsley with a mortar and pestle or in the bowl of a food processor, adding a pinch of salt and enough olive oil to create a loose sauce; if you make it ahead, store it in the fridge for up to a week.
Preheat your grill to medium-high and cook the steak for about 4 minutes, until a deep crust has developed on the bottom.
Flip and cook for another 4-5 minutes (for medium-rare) or until done to your liking.
Let the steak rest for 5-10 minutes before slicing and serving with the gremolata.