mall tuna baked in the oven with onions, cherry tomatoes and fresh oregano

Clean and wash the fish thoroughly. If you wish, remove their heads. Prepare the vegetables by cutting the potatoes into relatively small pieces so they will boil, and the onions and tomatoes. Wash the cherry tomatoes and the oregano. Place the potatoes, onions, tomatoes and cherry tomatoes in a Pyrex dish (or any other baking dish you have). Place the small tunas on top. Season with salt and pepper and rub the fresh oregano evenly over everything. Pour in the olive oil and bake in a preheated oven at 200°C for about 50 minutes.