Wash, stone and halve the plums. Mix egg, milk, oil, quark, salt, 100 g sugar and vanillin sugar. Mix flour and baking powder, sieve onto the quark mixture and knead with the dough hooks of the hand mixer.
Roll out the dough on a greased baking tray. Sprinkle with breadcrumbs and cover with plums. Bake in the preheated oven (electric: 175 °C/ gas: level 2) for 40-45 minutes. In the meantime, beat the egg white and lemon juice until stiff, pour in the remaining sugar.
15 minutes before the end of the baking time, spread the meringue evenly on the plums. Remove from the oven, allow to cool and serve dusted with icing sugar. Makes about 20 pieces.