Zingy lemon meringue bar

Instructions

1. Wash the lemon, chop into small chunks (leaving the skin on) and discard any seeds. Wipe your food processor clean then add the lemon. Process until the chunks have completely broken down, then add the lemon juice, egg yolks, cornflour and 125g of the sugar. Process until you have a thick, pale yellow mixture.
2. Set a small heatproof bowl over a pan of simmering water, making sure the base of the bowl doesn’t touch the water. Pour the lemon mixture into the bowl and stir continuously for 5 minutes, until the lemon mixture is gently heated through. Carefully pour into the baked pastry case and then transfer to a baking tray.
3. Preheat the oven to 200°C, fan 180°C, gas mark 6. In a food processor, blitz the ginger nuts to fine crumbs. Add the apple sauce and pulse until the crumbs are moist and just starting to come together. Tip into a 36cm x 12cm loose-bottomed rectangular tart tin and press the crumbs into the corners and up the sides to form even edges. Bake for 10 minutes until just starting to darken in colour. Remove them, then reduce the oven to 180°C, fan 160°C, gas mark 4.
4. Using a hand-held electric whisk, whisk the egg whites until soft peaks form. Gradually add the remaining sugar, whisking well between each addition, until you have a thick, glossy meringue. Spoon into a piping bag fitted with a star nozzle and pipe 12 rows of meringue onto the top of the tart to completely cover the filling.
5. Bake on the baking tray for 25 minutes until the meringue is golden. Remove from the oven and let cool for 3 hours before cutting into 12 bars to serve.