Cut open the vanilla pod, scrape out the pulp. Mix with sour cream, sugar and lemon juice. Whip cream until stiff and fold in. Chill for about 15 minutes. In the meantime, scrape out the seeds with a teaspoon of the pomegranate.
Cut off the edge of the cake if necessary. Cut the sponge cake into triangles. Wash the carambola, dab dry and cut into slices. Arrange vanilla sour cream, sponge cake and prepared fruits on plates, dust with icing sugar and decorate with mint.