Split the vanilla pod in half lengthways. Wash the guavas thoroughly. Put in a large pan and fill 3/4 full with water. Cook until the guvas change colour. Take off the heat and allow to rest for 10 minutes. Put it through a sieve lined with a muslin cloth into a bowl. Remove the pulp and seeds. Measure the volume of the juice and add twice its volumes to it in sugar. Pour the mixture into a stewing pot and bring to the boil. Take off the heat. Repeat this process 3 times. Allow to cool.