Prepare the apricots: Place the halved and pitted apricots in a large, heavy-bottomed pot. Add the reserved pineapple juice.

Cook the fruit: Bring the mixture to a boil over medium-high heat, stirring frequently. Reduce heat and simmer for 10 minutes, mashing the apricots slightly with a potato masher for a chunkier texture.

Add pectin and sugar: In a small bowl, whisk the powdered pectin into about 1/2 cup of the granulated sugar until thoroughly combined (to prevent clumping). Add this mixture to the fruit and stir well.

Boil vigorously: Add the remaining sugar and the lemon juice. Bring the mixture to a full rolling boil that cannot be stirred down. Boil hard for exactly 1 minute, stirring constantly.

Finish and skim: Remove the pot from the heat. Skim off any foam appearing on the surface using a metal spoon. Carefully stir in the drained crushed pineapple.

Jar the jam: Ladle the hot jam into sterilized jars, leaving 1/4 inch headspace. Wipe rims clean and seal with lids and bands. Process in a boiling water bath for 10 minutes for shelf stability, or refrigerate for immediate use.