Preheat the oven to 180 °C.
- Cut stockfish in 4 cm serving parts. Cut the onions, red onions and tomatoes in vedges.
Peel the potatoes and cut in half.
- Pour oliveoil in a casserole and heat to medium heat
Put stockfish, onions, red onions, tomatoes, potatoes, pesto and olives in layers in the casserole and cover with a lid.
- Put the casserole in the oven and let it bake for 20-25 minutes, until the onions, stockfish and potatoes are done.
Season wit salt and pepper.
Serve the casserole with bread.