1 lemon, juice and zest
700g/1lb 9oz rhubarb, cut into 2cm/ΒΎin chunks
260²µ/9ΒΌ΄Η³ϊ caster sugar
5 tbsp cornflour
flour, for dusting
butter, for greasing
3 free-range eggs, separated
300g/10Β½oz sweet shortcrust pastry