Knead the flour, butter, icing sugar, egg yolk and lemon zest into a smooth shortcrust pastry, cover and chill for approx. 30 minutes. In the meantime, wash the plums, dab dry, quarter and stone them. Roll out the short pastry on a floured work surface to a circle (approx. 30 cm Ø). Line a greased tart mould (25-26 cm Ø) with the dough. Cut off any protruding edges. Prick the base several times with a fork and spread with plum jam.
Cover the base with plum quarters, close together. Bake in the preheated oven (electric: 200°C/ gas: level 3) for 40-45 minutes. Heat apricot jam and pass through a sieve. Spread the finished tart with jam and sprinkle with sugar crystals. Best served lukewarm. Makes about 12 pieces