Place the cast iron skillet on the grill and heat it to 500 degrees Fahrenheit.

If necessary, filet the fish while the grill is heating up. After patting dry, season with salt & pepper.

Reduce the grill's temperature to 425°F, add the olive oil, and add the fish to the skillet after the cast iron is hot and the grill has reached 500°F. It can take a few minutes for the skillet's temperature to drop.

Close the grill and give each side two to three minutes to cook. The sides of the fish will begin to turn and pull away from the cast iron as you watch. You can determine when to flip it by doing so. Avoid flipping too soon.

Once the fish has been flipped, cook it for a further 1-3 minutes, or until it pulls up and turns white and flaky. The fish should have a lovely crispy skin produced by the hot cast iron and should be golden brown on both sides.

When ready to serve, take the fish from the skillet and brush it with the Garlic Butter.