Toast the almonds and pine nuts on low heat.
Let them cool a bit, then grind them in a food processor
In a bowl, combine the nut flour, the pastry flour, butter and sugar and mix until the dough comes together.
Cover with cling film and leave in the fridge.
For the filling, beat together the egg and sugar, then add the flour.
In a bowl squeeze the lemons, add some grated lemon zest and add enough water to reach 500 ml of liquid.
Add the liquid to the mixture of egg, sugar and flour.
Transfer the mixture into a saucepan and heat over medium heat, constantly stirring with a wooden spoon, until it comes to a boil. Set aside.
Preheat the oven to 180°.
Grease and flour single-portion tart pans.
Take the pastry out of the fridge.
Roll the pastry dough, then cut it into rounds and press them into the tart pans.
Stab a few holes in the bottom with a fork, then line the tart with foil and fill with dried beans.
Bake for 10 minutes, then discard the foil and bake for another 5 minutes or until golden.
When the tarts are ready, remove them from the oven, let them cool a bit and pour in the lemon mixture.
Garnish with whipped cream (optional).