Preheat the oven to 180°C/350°F/gas 4.Very finely slice 2 large aubergines and 1kg of mixed-colour tomatoes into rounds. Peel and very finely slice 1 red onion and 4 cloves of garlic. Trim 1 celery heart, halve, and finely slice lengthways. Throw it all into a large roasting tray with 1 tablespoon of dried oregano, 1 pinch of chilli flakes, 1 heaped teaspoon of baby capers, and 40g each of raisins and pine nuts.Crush 4 black olives with the heel of your hand, tear out the stones, then tear the flesh into the tray. Add 2 tablespoons of oil and a good pinch of sea salt and black pepper, then toss well. Arrange evenly, pulling a layer of tomatoes to the top, and bake on the bottom shelf of the oven for 40 minutes.Meanwhile, place 4 fish fillets in a sandwich bag, squeeze in the juice from 1 orange (reserving the halves), add a pinch of salt and leave aside.When the time’s up on the veg, remove from the oven and place 4 fish fillets on top, skin side up. Drizzle over the juice from 1 orange, then return to the bottom shelf of the oven for 15 more minutes, or until the fish is cooked through.Put the squeezed orange halves and 250g of wholewheat couscous into a bowl, just cover the couscous with boiling kettle water, then pop a plate on top and leave to fluff up.Sprinkle 40g of rocket over the gorgeous traybake, fluff up the couscous, season to perfection, divide it all up, and serve each portion with 1 tablespoon of yoghurt.