Scrub and clean the quinces well under running water to remove any fuzz from the skin.

Peel, quarter, and core the fruit, then rub each piece with lemon juice to prevent browning.

Cut into medium chunks and steam until tender.

Blend the cooked quince into a smooth purée using a food mill or blender.

Weigh the purée and return it to a pot with an equal weight of granulated sugar.

Cook over low heat, stirring constantly with a long-handled wooden spoon until the mixture thickens and pulls away from the sides of the pot.

Pour the hot membrillo into a parchment-lined dish or silicone molds for easy portioning.

Let it cool completely: membrillo sets within a few hours.

Unmold and cut into cubes, then coat each piece in granulated sugar for a classic finish (optional).