01 - Wash, hull, pit, and chop the fruit as required.
02 - Place the prepared fruit and lemon juice in a large, heavy-bottomed saucepan and lightly mash for a chunky texture or puree for smoothness.
03 - Stir in granulated sugar thoroughly and let rest for 10 minutes to extract juices.
04 - Heat the mixture over medium heat, stirring frequently to avoid sticking, until it reaches a full boil.
05 - Reduce heat to low and simmer, stirring occasionally, until the jam thickens and reaches 220°F (104°C), about 25–35 minutes. Skim any foam from the surface.
06 - If using, add vanilla bean or extract near the end of cooking and stir well.
07 - Spoon a small amount onto a cold plate; if it wrinkles when pushed, the jam is ready. Continue cooking and retesting if necessary.
08 - Pour hot jam into sterilized jars, leaving 1/4 inch headspace, then seal immediately.
09 - Allow jars to cool to room temperature before refrigerating or processing for extended preservation.