Ingredients

Step by step

1. Preheat the oven to 200°C, fan 180°C, gas 6. Unroll the pastry and lightly roll to make it a bit wider. Use to line a round 20cm fluted tart tin, 4cm deep. Chill for 30 minutes, then prick the base all over with a fork. Line with baking paper, fill with baking beans and blind-bake on a baking tray for 15 minutes. Remove the paper and beans; bake for a further 10 minutes.
2. Meanwhile, finely grate the zest from 1 grapefruit and set aside. Squeeze the juice from all 4 grapefruit into a measuring jug; top up with cold water to 750ml. Put the cornflour in a pan and gradually stir in the juice, then add 200g sugar and zest. Bring the mixture to the boil. Cook, stirring, for 1 minute. Cool for 5 minutes. Beat in the yolks and butter. Sieve into a bowl, then pour into the pastry case.
3. Reduce the oven temperature to 160°C, fan 140°C, gas 3. In a clean bowl, whisk the egg whites until stiff. Gradually whisk in the remaining sugar until stiff and glossy. Spoon the meringue on to the filling and use the back of a spoon to create swirls. Bake for 30-35 minutes until lightly golden. Leave to stand for 20 minutes before serving.
   Tip

   Be careful not to include any white pith when you are zesting citrus fruit, as it is very bitter and will affect the flavour of your dish.