On a nice day, pick the elderflowers in as unpolluted a place as possible and spread them out on a cloth at home so that the insects can crawl away.
Cut the stems as close as possible to the flowers and place in a container with the pineapple juice. Weigh down the flowers with a plate, cover the vessel and leave in a cool place for 2 days. Stir several times.
Strain the liquid through a cheesecloth after 2 days and mix with the preserving sugar and the scraped and chopped vanilla pod. Use a zest ripper or a kitchen knife to cut off the peel of the washed organic lemon and chop it up. Squeeze the lemon and add the juice with the zest to the jelly.
Cook the jelly according to the package instructions for the preserving sugar. A shot of rum is added shortly before the gelling test. Pour the jelly into sterilized jam jars. Close the jars and turn them upside down.