2. Place quince pieces in a large saucepan with lemon zest, vanilla, and cover with water. Bring to a boil and then reduce to a simmer. Cover with a lid and cook for about 30 minutes until quince is tender.
3. Strain the water from the quince. Discard the vanilla pod. Puree the quince in a food processor or blender. Measure the quince puree and use the same amount of sugar as a puree for the next step.
4. Return the quince puree to the pan and add the sugar. Bring the heat to medium-low and stir the puree with the sugar until the sugar has dissolved. Add the lemon juice.
5. Cook over low heat stirring occasionally for 1-1/2 hours until the quince paste is thick with a pink hue.
6. Line an 11 x 9-inch baking tray with parchment paper. Pour the quince into the tray and smooth the top with a spatula. Chill in the refrigerator overnight.