Place cleaned, prepared quinces in a large pot, then coat with lemon juice.
Add sugar and water then bring to a boil over high heat.
Once sugar is dissolved, reduce heat to medium and cook, stirring frequently, until quince pieces start to break down.
Using a potato masher, mash the quinces and cook for 30 minutes or until jam starts to get thicker.
Remove from the heat and stir in vanila seeds.
Set aside to cool to room temperature then preserve in sterilized jars by filling the jars as full as possible, seal the tops very well, then turn the jars upside down 'til cooled completely.