Preheat oven to 200°C. Grease 4 tart moulds lightly with melted butter.
Begin by making the pastry; rub the butter into the flour until it resembles fine breadcrumbs. Stir in the icing sugar and coconut and make a well in the centre of these dry ingredients. Mix the egg yolk, vanilla and 1.5 tablespoon of water, using a knife, bring the mixture together. If it appears a little dry, add a little more water to bind. Once you have a soft dough, wrap in cling film and place in the fridge to chill for 30 minutes.
Once chilled, roll the dough out thinly, about 2-3mm. Using a small plate or rim of a bowl, cut out circles of approx 12cm diameter. Gently press them into the tart moulds to line and trim off any excess pastry by rolling over the top of the tart tin rim with a rolling pin, prick the pastry all over with a fork. Bake the pastry blind by cutting 4 squares of nonstick baking paper and place these on top of the pastry, weighted down with ceramic baking beans. Place in the oven and cook for 15 minutes or until pastry begins to turn a deep golden colour. Then remove the nonstick baking paper and the beans and place back in the oven for a further 5-10 minutes to ensure pastry fully cooked and a nice deep golden brown colour. Remove and place to one side to cool.
To make the filling, in a saucepan place the lemon juice and zest, 75g caster sugar and butter and bring to the boil, then remove from the heat.
In a bowl whisk the eggs and 85g caster sugar well until the mixture begins to turn pale and increase in volume, this will take a couple of minutes.
Pour the hot lemon juice mixture over the eggs and continue whisking. Place back in the saucepan and bring back to the boil, stirring all the time with a wooden spoon. The mixture will thicken and turn glossy.
Once boiled and thick, pass the mixture through a sieve into a measuring jug, then divide between the four pastry cases and place in the fridge for 4-6 hours to set.
By toasting your desiccated coconut you intensify the flavour and improve your sweet pastry. This trick also works with nuts, a quick toasting on a baking tray for a few minutes brings out the natural flavours.
Make sure you use ceramic baking beans when you bake blind - they conduct the heat better and ensure the pastry cooks evenly.
Time saving tip
The tarts can also be set in the freezer if you are short of time, just remember to bring them out 30-40 mins before you want to serve them.