Preheat the oven to 200°C (400°F/Gas 6). Following steps 2–3, roll out and line a 25cm (10inch) fluted loose-based tart tin with the pastry. Blind bake the pastry shell, then remove it from the oven. Reduce the oven to 180°C (350°F/Gas 4).
Put the spinach into a sieve and squeeze out the water. Transfer the spinach to a bowl and combine with the salmon and eggs. Beat in the cream, then season with salt and pepper and a pinch of nutmeg. Pour into the pastry shell and bake for 30 minutes, or until the filling is just set. Leave in the tin for 5 minutes before serving.