How to make
Peel the quinces, cut them in pieces and remove the cores. Put them in a deep dish and add the water. Boil until tender (if necessary, add more water).
Pass them through a coarse sieve or blend. Combine the resulting mixture with the sugar and vanilla - boil on low heat to thicken it. Shortly before taking it off the fire, add the citric acid and mix well.
Distribute the marmalade into jars, keep them open overnight. Close them the next day, place parchment paper under the caps.
