Cut the fish in even portions (if possible, remove the bones). Sprinkle some salt and cover.

Peel the potatoes and slice them (half a centimer or so).

Wash the tomato, remove both ends and slice in three. Preheat your oven at 225 celsius (about 437F)

Rub the butter at the recipen you chose for the oven and dispose the potates so they cover the bottom. Sprinkle some salt, oil, oregano and pepper.

Add the tomato (sprinkle some more oregano on it). Add the fish and sprinkle some more pepper.

Cover with tinfoil and put into the oven. After 20 minutes uncover and put back into the oven. Check everything is cooked before serving.