Thinly slice the onion and the garlic.
Cut the courgette into half moon shapes and the peppers into strips. Roughly chop the tomatoes.
In a large casserole dish, heat some olive oil and cook the onion for 5 minutes. Add the courgette, pepper, garlic and herbs and sauté for 5 minutes. It’s important not to overcook them.
Add the chopped tomatoes and the vinegar. Season with salt and pepper.
Cover the pan and simmer over low heat for about 15 minutes or until the veggies are tender and the sauce is thick. Add a drop of water, if needed.
Put the fish pieces on top of the stew, season with salt and pepper. Put a lid on and steam for 5 minutes.
Serve with chopped basil or parsley leaves scattered on top.