Combine Chelsea Caster Sugar and one egg in a food processor until pale and frothy. Add Tararua Butter, Edmonds Standard Grade Flour, Edmonds Baking Powder and salt. Process until mixture clumps together in a ball around the blade. If dough is a little dry, add 1 Tbsp chilled water. Wrap dough in baking paper or cling film and chill for 30 minutes.
Grease a 24cm loose bottomed quiche/pie tin. Press pastry dough into the base and up the sides of the prepared tin. Chill again for 30 minutes. Preheat oven to 180°C bake.
Place a sheet of baking paper on top of pastry and fill with dry rice or baking weights. Blind bake for 20 minutes, until golden and crisp. Leave oven on. Whisk remaining egg and brush over pastry base while still hot.
While pastry is cooking, puree the feijoas and lemon juice and strain through a fine sieve to remove seeds. Combine water and Edmonds Fielder's Cornflour in a saucepan. Mix until smooth. Add egg yolks, Chelsea Caster Sugar, Tararua Butter, lemon zest and feijoa puree. Cook gently, stirring, until mixture thickens like custard (about 10 minutes). Set aside.
Beat egg whites until stiff peaks form. Gradually beat in Chelsea Caster Sugar until all incorporated and mixture is glossy and no longer grainy.
Pour filling onto cooked pastry then pipe or pile meringue on top. Bake for 15-20 minutes, until meringue is firm and golden. Cool in tin. Remove when cold and serve with whipped cream or ice cream.