Mix all the ingredients together (either with your hands or a food processor, until the mixture forms a smooth ball that comes off the bottom of the container.
Cover with clingfilm and let it chill in the refrigerator (for at least 15 mins).
Lower the dough to 4 to 5mm and prick the bottom of the pie.
Preheat the oven to 200°C.
Crumble
Place all the ingredients in a bowl.
Mix it all together until it becomes crumbly.
Cover with clingfilm and let it chill in the refrigerator.
Rhubarb compote
Peel the rhubarb and cut it into thin squares.
Place the rhubarb in a saucepan with the sugar, vanilla and lemon zest.
Cook it on a medium heat for 15-20 mins.
Pour into a bowl and allow to cool.
Assembling the tart
Coat the bottom of the pie with the almond purée.
Place the rhubarb compote evenly over the almond paste.
Cover the compote with the crumble.
Bake for 15 to 20 mins at 180°C, until the dough is cooked and the crumble has a golden color.