How to Make It
In a nonreactive saucepan, toss the peaches with the sugar and let stand, stirring, until the sugar is mostly dissolved, 1 hour.
Add the lemon juice to the peaches and bring to a boil, stirring until the sugar is dissolved. Simmer over moderate heat, stirring occasionally, until the fruit is glassy and the liquid runs off the side of a spoon in thick, heavy drops, 20 to 25 minutes. Skim off any scum that rises to the surface of the jam.
Spoon the jam into three 1/2-pint jars, leaving 1/4 inch of space at the top. Close the jars and let the jam cool to room temperature. Store the jam in the refrigerator for up to 3 months.