Pat the steak dry and place it on a baking sheet. Season liberally with the kosher salt, so that it looks like a light sprinkling of confectioner's sugar. Pepper, if desired. Let the steak sit at room temperature while you prepare a charcoal or gas grill for high heat (425° to 475°F), scrape the grate clean, and oil it lightly.
Grill the steaks over the hottest area of the grill for 3 1/2 to 4 minutes per side for medium rare. (To cook the steaks further, slide them to the coolest part of the grill and close the cover, then cook them for 1 to 4 minutes more). Let the steaks rest 10 minutes.
To serve, slice 1/4 inch thick, platter and slather on the romesco sauce, serving additional on the side.
Use this basic grilling technique on any premium grilling steak, such as rib steak( rib-eye when boneless), strip loin steak (aka New York steak), tenderloin or flatiron.