Pastry:Sift flour into a bowl, rub in butter, add egg yolk and water and mix to a firm dough. Do not overwork the dough. Cover and refrigerate 20 minutes. On a lightly floured bench, roll dough out large enough to line a 25-30 cm flan tin, trim the edges neatly.
Filling:Combine almonds, sugar, egg and lemon rind in a bowl and mix to a paste.
Spread almond mixture into pastry case, top with plums, dot with butter and sprinkle with extra sugar and cinnamon. Bake in a moderate oven for about 30 minutes or until golden brown. Dust with icing sugar and servewarm or cold with whippedcream and toasted almonds.