Preheat oven to 180°C.
In a small bowl, mix 4 tablespoons of olive oil with Fish Spice. Rub the mix over fish and refrigerate.
Peel the potatoes and slice into 1cm rounds. Place the potatoes, garlic, onion and 1 tablespoon of olive oil into a bowl. Cut one of the tomatoes in half and roughly grate into the bowl, discard the tomato skin and mix well. Season with salt and dried oregano.
Spread the vegetables across into the base of a large baking tray. Place the tray into the oven and bake for 30 minutes. The potatoes should be soft and almost cooked. After 30 minutes, remove the tray from the oven. Slice the remaining tomato and place it on top of the potatoes along with the olives and capers.
Place the marinated fish fillets on top of the vegetables. Put the tray back into the oven and bake for a further 20 minutes, or until fish and potatoes are well cooked.
