Prepare the fish: wash it and pat dry, season with a little salt and pepper and drizzle with olive oil. Stuff a couple of lemon slices and a few parsley stalks inside. Set aside.
Wash the bell peppers, cut them in half and remove the seeds. Roast in the air fryer with a drizzle of olive oil for 8 minutes, or in the oven for 15 minutes.
In the meantime, heat 2 tbsp of oil in a large skillet. Add the tomatoes and garlic and cook for 2-3 minutes. Press the tomatoes with a spatula to release their juices.
Add slices of potatoes and fry for 5-7 minutes until they have softened and browned lightly on the edges.
Add the bell peppers to the casserole. Season everything with salt, 2 tbsp of dried herbs and another drizzle of olive oil.
Place the fish on top. Pop in a couple more slices of lemon and parsley leaves.
Cover and simmer over low heat for 15-20 minutes. The flesh should be opaque (pick it with a fork to check). You can also send the casserole into the oven for 15 minutes over 190C.
To fillet the fish, transfer it to a cutting board. Use a spatula to pull the skin off from one side. Make a cut closest to the tail and tuck the spatula under the flesh. Slowly move it towards the head, sliding the flesh off the bones. Remove the central bone and the ones from the sides, the pull the skin off from the other side.
Serve the fish with vegetables and juices from the casserole, garnished with more fresh parsley and roasted pine nuts.