Steaks
Remove the steaks from the refrigerator and let stand at room temperature for 30 minutes. Meanwhile, combine the butter, harissa paste, parsley and zest in a small bowl; mix well. Transfer butter mixture to a sheet of plastic wrap. Wrap the butter, twisting the ends of the plastic wrap to form the butter into a 3-inch long log. Refrigerate until ready to serve.
Preheat the oven to 250 degrees F.
Season the steaks with the coarse ground sea salt and pepper and place on a shallow rimmed baking sheet. Bake until an instant-read thermometer inserted into the thickest portion of the steak registers 120F for medium-rare, about 33-35 minutes. Remove the steaks from the oven and let rest 5 minutes.
Heat a large cast iron skillet over high heat until very hot. Add a steak and sear until well browned, 1 minute. Turn the steak over and cook 1 minute longer. Repeat with the remaining steak. Serve immediately with potato salad.
Potato Salad
Combine the potatoes in a medium saucepan with enough cold water to cover by 2-inches. Bring to a boil over high heat, reduce the heat to medium and simmer until potatoes are tender but still hold their shape, about 10-12 minutes. Drain, transfer to a bowl and cool 5 minutes. Combine the anchovy, oil, lemon juice, cheese, garlic, salt and pepper in a separate bowl. Pour oil mixture over the potatoes add the romaine lettuce and toss gently to coat.
