For the pâte sucrée, sift together the flour, ground almonds, and 23g icing sugar. Add any of the almond that doesn't pass through the sieve back into the mixture.
Beat the butter and vanilla seeds until light in colour and soft, and then sift in the remaining icing sugar. Whip the sugar with the butter until light and fluffy.
Add the sifted dry ingredients to the bowl and mix until it resembles a sort of wet sand. Tip the bowl out onto your work surface, and press together.
To make sure all of the vanilla and sugar is evenly mixed, you will use a technique called 'fraiser' or 'fraisage'. Use the heel of your hand to smear the mixture together on the table, then scrape it off the table, fold it over itself, and continue smearing until it's evenly mixed (see image above).
Pat the dough into a disc, and wrap in cling film, Refrigerate for at least 30 minutes.
Preheat your oven to 325°F (162°C), grease and line a tart pan with a circle of parchment paper.
To roll out the dough, place the disc between two sheets of parchment paper. Roll out until it is large enough to fit your tart pan and lay inside*.
Press the dough into the corners and fluted edges of your tin, then trim the edge either with your fingers, or by rolling over with your rolling pin,
Line the tart with parchment paper, and fill with rice or beans.
Bake in your preheated oven for 10-12 minutes, or until the edges are starting to turn golden. Remove the beans and paper, and continue to bake for another 10-15 minutes, or until the bottom is golden brown. If the edges brown too quickly, cover them with some aluminum foil.
Remove tart from the oven and allow to cool slightly.
While the shell is baking, prepare the lemon sabayon filling.
Place a large heat safe bowl over a boiling bain marie, and whisk together the lemon zest, juice, sugar, and eggs.
Continue to whisk the mixture slowly, trying not to add too much air, until the sabayon is lighter in colour and thick. You should be able to draw a figure 8 on top with the mixture and it'll sink slowly. If the mixture is heating too quickly, don't whisk more, simply take the bowl on and off the heat to prevent it from getting too warm.
Remove from the heat, and whisk in the cubed butter, a little at a time. Preheat oven to 300°F (148°C).
Pour the mixture into your tart shell, and bake in the preheated oven for 10+ minutes, or until the sabayon forms a skin, and the tart is set but jiggles a bit in the middle.
Allow tart to cool before removing from the tin, and decorating with fresh fruit or a dusting of icing sugar, if desired.