Cut the nectarines into pieces, transfer to a baking tray lined with baking paper.
Bake for approx. 20 mins. in the centre of an oven preheated to 220°C, remove.
Squeeze the juice from the lemon, finely chop the basil.
Mix the nectarines, sugar, water, lemon juice and basil in a pan, bring to the boil while stirring, boil fast for approx. 4 mins.
Puree the jam, skimming off any foam.
To fill the jars
Ladle the jam into the clean, pre-warmed jars while still boiling hot, fill the jars to just below the rim, seal immediately. Briefly upend the screw-top jars, leave to cool on a towel.