Combine the quartered apricots and lemon juice in a large, non-reactive pot. Cook over medium heat, stirring occasionally, until the fruit softens significantly and releases its juices (about 10-15 minutes).

If you prefer a smoother jam, carefully use an immersion blender to pulse the mixture a few times until it reaches your desired consistency. Do not over-blend if you like whole fruit pieces.

In a separate small bowl, whisk the powdered pectin into 1/2 cup of the granulated sugar until no lumps remain. This prevents lumping when added to the hot fruit.

Increase the heat to high. Sprinkle the pectin-sugar mixture over the boiling fruit, stirring vigorously for 1 minute. Immediately add the remaining granulated sugar, stirring constantly until it is fully dissolved.

Bring the mixture to a rolling boil that cannot be stirred down. Boil hard, stirring frequently to prevent scorching, until the jam reaches 220°F (105°C) on a candy thermometer, or passes the cold plate test (about 5-10 minutes after the hard boil begins).

Remove from heat. Skim off any surface foam using a metal spoon. Ladle the hot jam carefully into sterilized hot jars, leaving 1/4 inch headspace. Wipe rims clean and seal with lids and bands.

Process the sealed jars in a boiling water bath for 10 minutes to ensure a proper seal. Remove jars and let cool completely before checking seals.