Preheat the oven to 200°C/gas mark 6. Mix together the walnuts, honey, vinegar and za’atar. Place the salmon fillets on a baking tray lined with greaseproof paper. Top each fillet with the walnut mixture, pressing down so it coats the skin. Bake in the oven for 12-15 minutes, until golden and crispy on top and the fish is opaque.
Meanwhile, boil the cauliflower florets for 10-12 minutes until soft. Drain and return to the pan. Cook over a gentle heat for a couple of minutes to dry it out. Add the goat's cheese and mash with a potato masher, then season with black pepper.
Meanwhile, steam the tenderstem broccoli for 8-10 minutes. Serve with the salmon and mash.