Tarte au citron- vegan

After the festival, we had a multitude of lemons to use up, so what could be better than this vegan twist on the French classic? It's very tangy, so you might like to include more sugar in the pastry case to compensate.
Case:
300g wholemeal plain wheat flour
150g unhydrogenated vegan margarine
1 tab demerara sugar
Filling:
6 lemons, juiced (make juice up to 300ml if necessary with water)
finely-grated lemon peel to decorate
5 1/2 tabs unrefined icing sugar
2 tsps lemon extract
100g unhydrogenated vegan margarine
2 tabs agar flakes

• First make the pastry case: rub the fat into the flour and sugar and mix to a dough with a little cold water.
• Roll out on a floured surface 3-4mm thick (not too thick)
• Line a greased flan dish/ shallow springform cake tin with the pastry and bake blind until crisp but not overbrowned at 200C.
• While the pastry case is in the oven, prepare the filling: mix the sugar and margarine with the lemon juice and lemon extract using a balloon whisk, then whisk in the agar flakes. Heat gently, stirring from time to time to dissolve the agar flakes. Let it simmer like this for 3-5minutes (or follow the instructions on the agar packet).
• To assemble, pour the filling into the cooked pastry case (it does not have to be completely cooled) and cool/ refridgerate until set. Mine turned out the consistency of lemon curd.
• Sprinkle with the grated lemon peel.
• Possible tweaks: Add ground almonds to the pastry and press into the bottom of a flan dish like cheesecake base. Or you could try adding the almonds to the filling mixture: I've seen some recipes which include this.You could even decorate the top with dark chocolate shavings. A sugar-free version could be made by substituting the sugar for agave nectar.