Cook the potatoes and onions in boiling water for 5-7 mins. Drain, then gently mix with the thyme, anchovies and some black pepper.

Meanwhile, heat the oil in a pan and cook the pepper, covered, for 5 mins. Add the tomatoes, vinegar, bouillon and garlic, and cook for 8-10 mins more, uncovered, until the tomatoes have softened. You don’t want this to be too wet, so continue to cook until any excess liquid has evaporated, if necessary.

Heat the oven to 200C/180C fan/gas 6. Lay the cod loins in a shallow ovenproof dish and spoon over the tomato mixture, then the potato and onion mixture, in even layers. Sprinkle over the cheese. Bake for 30 mins until the cheese is golden and the fish is flaking but moist. Serve with the spinach on the side.