Make the pastry base. Beat the Chelsea White Sugar and egg in a food processor until pale and frothy. In another bowl, mix together the butter, flour, salt and baking powder and add to the egg and sugar mixture. Process until the mixture clumps together in a ball around the blade. Chill for 30 minutes, then press into the base and up the sides of a 23 cm loose-bottomed quiche or cake tin. Chill again for 30 minutes and preheat oven to 180ºC. Bake blind for 20-25 minutes until golden and crisp. Turn the oven temperature down to 130-150ºC.
Now to the filling. Mix all the ingredients together and pour into the cooked pastry shell.
For the meringue topping, beat the egg whites until stiff peaks form. Gradually beat in the Chelsea Caster Sugar until it is all incorporated and the mixture is glossy. Pipe or pile onto the filling and bake at the reduced temperature for 20-25 minutes until the meringue is firm and crisp. Cool in the tin. Remove when fully cold and serve with whipped cream or ice-cream. Cut with a wet knife and wipe the knife between cuts to neaten the slices.