2. Step
Heat oil in a large cast-iron or heavy-bottomed skillet over medium heat. Add the fillets and cook, undisturbed, until starting to brown on the bottom, 3 to 5 minutes. Flip and reduce heat to medium-low. Cook, undisturbed, until the tops and bottoms of the fillets are dark brown and the fish flakes easily with a fork, 4 to 6 minutes. Serve with lemon wedges, if desired.