Pour this deliciously light sauce over a grilled steak for an simple but filling dinner.
Season each side of the steak with 1 tsp. kosher salt. Let stand at room temperature for 1 hour.
Cut the peel off the lemon, leaving a thin layer of the white pith. Halve and juice the lemon. In a food processor, coarsely chop the lemon peel into pieces that are about 1/4 inch in size. Add the parsley and the remaining 1 tsp. kosher salt; pulse until coarsely chopped, 2 to 3 pulses. Transfer to a small bowl. Stir in the lemon juice and oil.
Heat a grill or a grill pan over high. Add the steak; cook until charred in spots and cooked to medium to medium-rare, 2 to 4 minutes per side, depending on the thickness of the steak. Let rest for 10 minutes. Thinly slice the steak against the grain. Toss with the sauce or pour the sauce on top.