Step 1

Set a heavy cast iron or stainless steel skillet over medium-high heat until very hot but not smoking, about 3 minutes.

Step 2

While the skillet is heating, wash the fillet, then pat it really dry with paper towels. The drying part is critical, otherwise, the skin won’t get crisp. Season both sides of the fish fillet with salt and black pepper.

Step 3

When the skillet is hot, carefully add just enough ghee or oil to evenly coat the skillet. Wait a few seconds for the oil to heat and then quickly add the fish, skin side down. The fillet will contract and curve upwards. When this happens, take a flexible spatula and press the entire fillet gently back down and hold for a few seconds to ensure even cooking and crisp skin all over. Let the fish cook without messing with it too much until you can see a golden brown color on the edge of the skin and the edges of the fish flesh become opaque, 3 to 4 minutes.

Step 4

Carefully and gently use a spatula to lift up the fillet and flip it over. Add the butter, if using, and baste the fish until cooked through, 2 to 3 minutes longer.

Step 5

Gently transfer the fish to a plate and serve with a squeeze of lemon.