Combine apricots, sugar, and lemon juice in a pot over medium heat; add butter to reduce foaming. Bring to a rolling boil, stirring constantly. Quickly stir in pectin; return to a full boil for 1 minute. Remove from heat; skim foam.
STEP 2
Inspect jars for cracks and rings for rust. Sterilize jars and lids in boiling water for 5 minutes.
STEP 3
Pack jam into hot jars, filling to 1/4 inch from the top. Remove air bubbles and wipe rims. Screw on lids tightly.
STEP 4
Place jars in a large stockpot filled with water. Boil and cover jars with an additional 1 inch of water. Process for 5 minutes.
STEP 5
Remove jars, place on a cloth-covered surface, and let rest for 24 hours. Ensure seals are tight. Store in a cool, dark area.