The recipe for this is in the wonderfully comprehensive Leith's Cookery Bible, which, frankly, I find of invaluable assistance. This recipe is adapted from the 2003 edition.
For the pate sucree (made the trad way)
170g plain flour
A pinch of salt
85g unsalted butter, softened
3 egg yolks
2 drops of vanilla essence (I would use extract here)
Sift the flour with the salt on to a board. Make a large well in the centre and put the butter in it. Place the egg yolks and sugar on the butter with the vanilla essence.
Using the fingertips of one hand, mix the butter, yolks and sugar together. I learnt on the course that this is called pecking. After that, chop in the flour. When combined, frasier the pastry. This involves shaving slivers off the ball of dough with a pallet knife, and then pressing all the slivers together to form your finished clump of pastry.
If the pastry seems too soft, wrap it in clingfilm and chill in the fridge. Then, roll it out to fit your tin, and chill again before baking. I recommend blind baking (I nearly mispelled that as "bling baking", which is something completely different) this tart case for about 15 minutes. You can remove the baking beans, or whatever you're using, for a bit to give the bottom a short flash of heat. The crust should be lightly golden and smelling shortbready when you remove it from the oven.
For the complete tart
Pastry - in the quantity set out above
1 egg yolk
170g caster sugar
150ml double cream
Grated zest and juice of 2 lemons
Icing sugar, sifted, for dusting
Firstly, preheat the oven to 190 degrees C/375 degrees F/gas mark 5.
Make the filling by mixing the eggs and egg yolk with the sugar until smooth. Pass through a sieve. Stir in the cream and add the lemon zest and juice. The mixture will thicken considerably, but fear not. The filling is best made the day before and left in the fridge to mature. Make sure you taste it again before cooking, and add more lemon if necessary.
Pour the filling into the pastry case. Bake in the oven until it is almost set but still wobbles attractively when given a light shove.