Season the flesh side of each fillet heavily with salt. I use about 2 tablespoons total for 2 pounds worth of fillets.
Place the fillets in a dish, skin side up, cover and refrigerate for one and a half hours.
Preheat a large cast iron skillet on medium heat.
Rinse the fillets well with cool water and pat dry.
Melt the butter and sear the salmon skin side down first for approximately 5 minutes.
When the skin releases easily from the hot skillet, flip and cook for an additional 4 minutes.
Transfer to a plate and drizzle with freshly squeezed lemon.
Notes
You can skip the rinsing off the salt and simply pat the fillets dry. I do, however, find them to be quite salty if you don't rinse them first.Check the internal temperature of the salmon before consuming it. Salmon should be cooked to an internal temperature of 145°F.