1) Preheat the oven to fan 180C gas 6. 2) Put the potatoes, celeriac and lemon juice in a bowl and toss to coat well. 3) Add the nutmeg to the cream and stir well. 4) In a large ovenproof dish, put a layer of potato and celeriac. Top with a layer of salmon, onion and dill. Drizzle with a little cream and season well. 5) Repeat, and then top with a final layer of potato and celeriac. 6) Pour the remaining cream evenly over the top. 7) Cover the tray with foil and bake for 45 minutes. 8) Remove the foil and bake for another 35 - 40 minutes until golden and cooked through. 9) Leave to cool for a few minutes before serving.