Wash the quinces thoroughly under running water to remove any fuzz, then peel, halve, and scoop out the cores, discarding seeds and tough center.

Cut the peeled quince halves into roughly one-inch chunks to ensure even cooking.

Place the quince chunks and 1 cup water into a large pot and bring to a boil over high heat.

Reduce heat to medium and simmer for 20 to 30 minutes, stirring occasionally, until the quince pieces are completely soft and fall apart under the spoon.

Pour the softened quince and cooking liquid through a food mill into a large bowl to create a smooth puree.

Return the quince puree to the pot and stir in 1.5 pounds granulated sugar and 2 tablespoons fresh lemon juice until fully dissolved.

Increase heat to medium-high and bring to a rolling boil, stirring frequently, then cook until the mixture reaches 220°F on a candy thermometer, about 60 to 90 minutes.

Test for doneness by placing a spoonful on a cold plate, cooling for one minute, and checking that the surface wrinkles when pushed with your finger.

Sterilize glass jars by running them through the hot dishwasher cycle or boiling in water for 10 minutes; remove with a jar lifter.

Ladle the hot jam into the jars, leaving 1/4 inch headspace, wipe rims clean, apply lids and bands, and process in a boiling water bath for 10 minutes.