Heat broiler to high with rack set 6-inches from element.
Arrange salmon fillets skin-side down on prepared sheet; pat dry and season with ½ teaspoon kosher salt and ¼ teaspoon black pepper.
Broil salmon until mostly opaque but center still looks undercooked, tops are charred, and an instant-read thermometer inserted in the centers registers 125ºF (48–52ºC), 10–12 minutes.
If you're using Diamond Crystal kosher salt, use 3/4 teaspoon. For the best results, use a thick salmon fillet, preferably center-cut, at least 1-inch thick. You will likely need to buy farm-raised instead of wild-caught for this recipe. In that case, look for USA farm-raised salmon with no added coloring. The USDA recommends cooking salmon to an internal temperature of 145ºF (63ºC). We prefer to under-cook it a bit and remove salmon from the heat when it reaches an internal temperature of 125ºF (52ºC).