Segui i passaggi nell ordine indicato.
In a substantial, heavy-bottomed pot, combine the fresh blueberries, bright lemon juice, and granulated sugar.
Stir the ingredients thoroughly to ensure everything is well-mixed and evenly distributed.
Place the pot over high heat and bring the mixture to a rapid, rolling boil that cannot be stirred down. Maintain this vigorous boil for precisely one minute, stirring continuously throughout to prevent sticking.
Carefully remove the pot from the heat. Incorporate the powdered fruit pectin, stirring diligently until fully dissolved. Skim off any foam that forms on the surface to ensure a clear jam. Stir once more and repeat the skimming process if necessary.
Ladle the piping hot jam into clean, sterilized canning jars, leaving exactly 1/4 inch of headspace at the top. Process the filled jars in a boiling water bath for 10 minutes to ensure proper sealing and long-term preservation.