Cut peach skin crosswise. Blanch briefly in boiling water. Remove, rinse with cold water and peel off skin. Halve the fruit, remove the stone and cut the flesh into small cubes. Weigh 950 g, mix with jam sugar, rum and lemon juice in a large pot.
Heat while stirring and bring to the boil. Let simmer for about 4 minutes while stirring. Possibly make a gelling test. Fill jam full to the brim into clean, hot rinsed glasses with twist-off lids and close them tightly. Let it cool down.