Sieve the flour and sugar and rub in the butter until the mixture resembles breadcrumbs.
Beat the egg with four tablespoons of ice-cold water.
Mix the liquid into the flour to form a dough without overworking it.
Knead the dough lightly, wrap in film, and refrigerate for 30 minutes.
Beat butter and sugar then whisk in eggs and almonds to make the frangipane.
Preheat oven to 180°C and roll the dough to line a 25cm tart ring.
Spoon frangipane into the pastry case and arrange plums over the top.
Bake for 30 to 40 minutes until the pastry is golden and fruit is tender.
Dust with icing sugar and serve warm with cream or crème fraîche.