For the base: Preheat oven to 160C. Line a 23cm tart shell with pastry,rest at least 1 hour then blind bake (see tip) for 20-25 minutes. Remove foil,brush with the 1 beaten egg mix,return to oven for 3 minutes or until golden and cooked through. Cool on rack.
For the lemon curd: Melt butter in a heavy-based saucepan,add 330g sugar and combine. Add lemon juice and 6 eggs,cook over medium to low heat,stirring continuously for about 10 minutes,until mixture has thickened and coats the back of a spoon well. Don't boil mixture or eggs will curdle. Remove from heat,pass through a sieve into clean bowl. Cover with cling film and cool in fridge.
For the Italian meringue: Put remaining sugar and water in saucepan and stir to dissolve. Brush down sides of saucepan with a clean,wet pastry brush to prevent crystallisation. Bring to boil (117C) or until soft ball forms when a dollop is dropped in iced water. Meanwhile,whisk egg whites to soft peak. Pour over syrup and continue to whisk on a high speed until cool and firm peaks have formed.
To assemble: Spoon the curd into tart shell. Spoon or pipe meringue on top. Before serving,glaze with blowtorch or under very hot grill to golden brown.