Roughly chop the chocolate and melt it with the butter in a saucepan over low heat. Let cool down to room temperature.
Preheat the oven to 180 degrees (160 degrees circulating air). Grease a springform pan (26 cm Ø), dust with flour and refrigerate. Peel the apples, cut into wedges, core and dice, mix with a little orange juice. Beat the eggs with sugar and salt until frothy.
Mix the flour with cocoa powder and baking powder, and stir into the egg mixture with the butter-chocolate mixture. Pour the dough into the prepared pan, smooth it out and spread the apple cubes on top. Bake the cake in the preheated oven for about 50 minutes.
Remove the cake and let it cool down a little. Put the jam through a sieve, heat it and brush the cake with it. Let cool down completely.
Serve the cake with a little whipped cream.