Preheat the oven to 180 degrees C. Pit the cherries and cut them in half.
Scrape the vanilla pod and glaze the stalk with a little sugar in a frying pan. Extinguish with half of the cherry juice and boil down to a creamy consistency. Add to the cherries and simmer for about 2 hours with the lid closed.
Cut the pumpernickel into small pieces and dry in the oven for about 10min, turning occasionally to the other side.
Beat the eggs with 100g sugar and cinnamon until creamy and fold in the flour with the baking powder. Grate the chocolate very finely and fold into the batter with the pumpernickel crumbs. Bake the dough in a cake springform pan lined with parchment paper in a heated oven for 20 minutes, remove from the pan and place the dough base on a plate to cool. Soak the gelatine in a little water for 10 min. Squeeze the gelatin and let it melt in the remaining hot cherry juice. Put back some nice cherries. Spread the other cherries evenly on the cake base as they set.
Chop a few lime zests very finely and stir them into the curd with the vanilla sugar and spread evenly on the firming cherry layer. Set in the refrigerator and garnish with the reserved cherries.