For cherry-nectarine jam, pit cherries, remove pits from nectarines and cut into pieces. Mix with jam sugar and let stand in the refrigerator for about 2 hours.
Heat jam jars in the oven at 140 degrees convection. Simmer in a large saucepan for about 5 min., puree briefly with a hand blender.
Simmer for another 2 minutes, pour into the hot jars and seal immediately.
Preparation Tip:
If you don't want chunks in the cherry-nectarine jam, just puree the fruit very finely.