I have wonderful memories of this when I was a child, when we called it wang wang pie.
Pastry;
2 c plain flour, 1/4 tsp salt, cold water
Sift flour and salt, cut in butter and mix until a stiff dough. Put in fridge.

Filling, mix together in saucepan over gentle heat for 5-10 mins:
1/4 c cornflour
2 Tb custard powder (optional)
3/4 c sugar
2 tsp lemon rind
1/4 c lemon juice
3 egg yolks
1 Tb butter

Meringue, beat together:
1/4 c caster sugar
1/4 tsp vanilla
3 egg whites

Roll out pastry, line 20cm flan tin. Cover with foil and blind bake for 20 min at 190 C.
Remove foil and return to oven for 5 mins.
Pour filling into pastry, spoon over meringue. Bake until cooked through, about 15 mins.

Here's a mini pie Mama Chan made: