Rinse the salmon fillets, then pat dry with paper towels.
Rub salt and pepper on all sides of the salmon.
Heat the olive oil in a 10-inch cast-iron skillet until nearly smoking hot.
Lower the heat to medium, then add the salmon fillets, skin side down.
Cook until the skin is golden brown or the fillets release easily from the pan.
Using an offset spatula, flip the salmon and cook the second side for 3-4 minutes.
Remove the salmon from the pan and place on a plate to rest. If you have a wire rack, that’s even better — the skin will continue to crisp instead of being steamed from the plate.
Turn off the heat on the skillet.