Mix flour, 1 teaspoon of sugar, salt and lemon zest in a bowl. Add the eggs and milk and mix to a smooth dough with the whisk of the hand mixer. Melt the fat in a saucepan and stir into the dough.
Heat the oil in portions in a small pan. Gradually bake 8 crépes from the dough and keep warm. Drain the plums on a sieve. Collect the liquid. Melt the remaining sugar in a dry pan without fat.
Remove the pan from the heat and deglaze the caramel with the prune juice. Let it boil while stirring until the caramel has dissolved. Wash the apple, quarter it and cut out the core. Cut the apple quarters into thin slices.
Add drained plums and apple slices to the caramel sauce. Season with slivovitz. Fold the crépes together and arrange two on each plate. Pour plum-caramel sauce over them. Serve dusted with icing sugar.