Beat the eggs with half of the sugar and the vanilla sugar until fluffy.
Sift the flour and baking powder into the wet ingredients, then stir in the melted butter.
Line a cake pan with parchment paper, then butter the bottom of the pan. Sprinkle the remaining sugar over the bottom of the pan.
Drain the pineapple slices. Line the bottom of the pan with the pineapple slices. Pour the batter over the slioces and bake the cake in a preheated oven (180°C or approximately 350°F, center rack) for about 35 minutes.
Remove the cake & allow to cool. Turn the cake onto a plate, remove the parchment paper and serve garnished with currants.