Heat a 12-inch heavy-bottomed skillet for 3 minutes over high heat.
Sprinkle fillets with salt and ground black pepper.
Add oil to pan; swirl to coat.
When oil shimmers (but does not smoke) add fillets skin side down and sear for 30 seconds, being careful not to move them around in the pan.
Reduce heat to medium-high and continue to cook until skin side is well browned, about 4 1/2 minutes.
Turn fillets and cook until firm, but not hard.
Remove fillets from pan and let stand 1 minute.
Serve with a squirt of fresh lemon or lime.