Place the flour, salt and icing sugar in a bowl and create a well. Add the cubed butter and mix on a low speed until it resembles breadcrumbs, about 2 minutes.
Add the eggs and slowly mix just until the dough starts to clump together. Shape into a flat disc, wrap in cling film and chill in fridge for a few hours.
To make the filling, zest and juice the lemons and whisk these together with all of the remaining ingredients, until you have a smooth consistency.
Roll out the pastry on a floured surface until it is about the thickness of a pound coin. Cut out circles slightly larger than your mini tart tins and gently push the pastry into the corners. Trim off any excess.
Freeze for 15min and then blind bake for 12min at 160C or until golden around the edges. Once golden, remove the baking beans, egg wash and bake for a further 5min.
Once the shells are cooked, gently use a microplane to smooth the edges. Pour in the lemon filling and bake at 110c for 20-30min. After 20min check every few minutes. There should be a tiny wobble in the centre of the tart. Allow to cool completely.
To make the meringue, add the egg whites to a stand mixer on a low speed. Meanwhile, heat the sugar and water until it reaches 118C. At this point the egg whites should be at soft peaks. Pour the sugar syrup into the egg whites and whisk on high speed until the bowl has completely cooled.
Pipe the meringue on to the tart and gently toast with a blow torch.