This is a simple and quick way to cook a whole fish - and it really lets the flavour of the fresh fish sing! Taking the extra 10 minutes to do a quick brine ensures that the fish is evenly seasoned throughout. Use any combination of fresh herbs you have on hand.
Preheat oven to 200°C/400°F. Add the salt to a large mixing bowl along with 1 litre (4 cups) of water. Stir to dissolve the salt and then add the fish. Allow the fish to soak in the water for 10 minutes.
Thoroughly dry the fish and discard the water. Rub the skin with 1 tbsp of olive oil and place on a large piece of aluminium foil. Place the lemon slices and herbs into the cavity of the fish. Drizzle the fish with the remaining tablespoon of olive oil and season generously with salt and pepper. Crimp the foil tightly around the fish and move to a rimmed baking tray.
Move to the oven and cook until the fish registers at 55°C/130°F when an instant-read thermometer is inserted into the thickest part of the flesh - about 25 minutes (see notes). Allow the fish to rest for 10 minutes before serving.
Notes
You can check the temperature by piercing directly through the foil - no need to un-crimp. This makes it easier to return to the oven if it still needs to cook longer.