Step 1 Begin by making the pastry :
Sift theflour, cornstarch and sugar. Cut into cubesor grate the cold butter and work it by hand. You can optionally pulse this mixture in a robo until you have crumbs the size of small peas.Add in the eggs. Then gently fold the mound of ingredients together until you have formed a ball of dough.
Step 2 Wrap with plastic film then place in the refrigerator for least one hour to firm up the dough.Once the hour has passed, lightly grease your work area then dust generous with flour. Now flour also your rolling pin.Pre-heat the oven.
Step 3 Roll out the dough by rolling then turning the dough after each turn. Continue rolling until you have the right size to fit your dish. The thickness should be about 1 cm or half inch. If there is any overhanging pastry, cut it away.
Step 4 Save the dough in a bag in the freezer for next time or mini tarts. Prick the pastry with a fork then lay a piece of parchment, wax paper or foil on the pastry. Now lay in some dry beans or baking weights.
Step 5 Bake the pastry in the oven at 170° for about 15 minutes. Remove the pastry and allow to cool, before filling. Do not turn off the oven at this point but lower to 150°.
Step 6 Lemon curd filling:
Roll the lemons on the work area, in preparation to extract the most juice out of the lemon.With a zester or fine side of a grater, remove the outer skin or zest of the lemon. Be careful not to remove the white pith - that is bitter. Squeeze the juice from the lemons.
Step 7 In a bowl, beat the egg yolks with the sugar until creamy (or lemony coloured)In a double - boiler melt the butter. Add the salt and sugar to the melted butter, then stir in the lemon mixture. Cook over low heat, stirring constantly for 3-4 minutes.
Step 8 When the sugar has completely dissolved, remove the double boiler from the stove.To temper the eggs and prevent their curdling, pour off about 1/3 cup of the hot lemon mixture into the beaten eggs and whisk it quickly.
Step 9 Use the whisk to stir up the lemon mixture (in the top of the double boiler) and while the mixture is moving rapidly, slowly pour the egg mixture in a thin steady stream, stirring all the while. Return the double boiler to low heat.
Step 10 Cook, whisking constantly for about 10 minutes or until the curd thickens and takes on a glossy sheen with the consistency of honey. Mixtures continues to thicken upon standing. Allow to cool before spooning it into the tart pastry.
Step 11 Merginue:
Use a large, roomy bowl and in it whisk the egg whites until they form stiff peaks. Using a electric beater or stand mixer would be easiest but by hand is fine also! Now whisk in a quarter of the sugar at a time until it is all incorporated. At this stage you can simply spread the meringue to the very edge of the pastry rim with a palette knife. Or you can fill the merginue into a pastry bagand pipe designs on the tart. Place in the oven and bake on the centre shelf for 45 minutes, by which time the meringue will have turned a pale golden colour - almost brownish gold, and be crisp on the outside and squashy in the inside.