Cook the chopped, peeled, and pitted peaches with the juice of one whole lemon in a medium or large pot over medium heat.

After 5 minutes start mashing with a potato masher or fork while stirring occasionally. Add the sugar and keep cooking, stirring and mashing. 

After adding the sugar, cook for 15 or 20 additional minutes, mashing and stirring to achieve desired consistency.

Allow the jam to cool and store in the fridge in sealed containers.