Crush the biscuits to make fine crumbs and stir into the melted butter.
Press the warm buttery crumbs over the base and up the sides of a 25cm round, 4cm deep, pie plate or flan dish. Chill for 15-20 minutes until firm.
Spread the base of the tart with 2 tbsp of the Lemon Curd. Stir the remaining Lemon Curd into the fresh raspberries, crushing them lightly to release some juice, then spoon them over the tart base.
Whisk the egg whites in a large, clean mixing bowl using an electric mixer until stiff peaks form. Gradually add the caster sugar, 1 tbsp at a time, whisking well after each addition, bringing the whites back to stiff peaks before you add more sugar. Once you've whisked in half the sugar, add the rest in larger quantities. When all the sugar has been added, whisk the meringue back to glossy, stiff peaks, then whisk in the vinegar and cornflour.
Spoon the meringue into a generous mound over the fruit and swirl into peaks with the back of a spoon.
Caramelise the meringue under a hot grill for 30 seconds or with a cook's blowtorch.
Keep the tart in a cool place and serve within 1 hour.
This recipe is party-sized but it's very easy to half the quantities for 4-6 servings. Use an 18cm pie plate.
To make ahead, make the biscuit base and the raspberry filling the day before and keep cool. Add the meringue about an hour before using.
When in season, use a mix of summer berries for the filling.
Try using ginger nut biscuits for the base for a touch of spice that's delicious with lemon.