Rinse the cranberries thoroughly under cold water and remove any stems or bad berries.
In a large pot, combine the water and sugar over medium heat. Stir until the sugar dissolves.
Add the cranberries and lemon juice to the pot. Bring the mixture to a boil, then reduce the heat to low.
Simmer the mixture for about 20-30 minutes, stirring occasionally. The cranberries will burst and the mixture will thicken.
If you like a smoother jam, blend the mixture using a food processor or blender until you reach your desired consistency.
Add cinnamon during the last few minutes of cooking for added flavor, if desired.
Once thickened, remove from heat and let it cool slightly.
Pour the jam into sterilized jars, leaving about half an inch of headspace. Wipe the rims of the jars to ensure a good seal.
Place jar lids and rings on the jars and process in a boiling water bath for 5-10 minutes for preservation, if desired.
Allow the jars to cool completely before storing them in the refrigerator or pantry.