Place the cranberries, sugar, and lemon juice in a medium saucepan.
Bring the berries to a boil over medium high heat. Reduce heat to medium and simmer to break up the berries, approximately 15 minutes.
Use a potato masher or fork to mash the fruit as much or little as desired.
The jam will be somewhat thick. Add water if needed to get your desired consistency. Add more sugar if it is too tart for your liking.
Store in a jar in the refrigerator for up to three weeks. Or freeze.
Notes
The volume you get will vary with how long you cook it (how thick it is) and how much you mash it.This will roughly fill one pint sized mason jar, which is perfect for storing in the refrigerator.