Preheat the oven to 170°C. Cut the apricots in half, carefully remove the stones. Half the apricots again to get wedges.
Separate the eggs.
Beat the butter, powdered sugar and vanilla sugar until light and creamy, then stir in the egg yolks.
Mix the flour with the baking powder, add this to the butter mixture and combine gently,
Beat the egg whites with the granulated sugar until you get a hard foam, then fold this into the batter with a spatula.
Grease a baking tray then transfer the batter into it. Spread it evenly around the tray with the spatula.
Put the apricot pieces on the top, slightly pushing them into the batter.
Put the tray into the oven and bake for 45 minutes.
Let it cool then cut it into slices. Dust the cake with icing sugar before serving.
Serve with custard if you like.