1. Dredge the steak with the flour. Press the rosemary into the fish and brush with oil.
2. Heat five tablespoons of the butter in a skillet, add the fish and cook, turning once, until the fish flakes easily when tested with a fork, about fifteen minutes. Sprinkle with salt and remove the fish to a hot platter.
3. Add the wine and remaining butter to the pan and heat. Pour over and around the fish.