Sterilize jars and lids according to safe canning practices.
Place peppers in a blender with the apple cider vinegar and pulse until peppers are minced.
Pour the pepper-vinegar mixture into a saucepan. Add sugar, pineapple juice, salt and butter. Stir well until dissolved. Bring to a boil. Cook for about 10 minutes while stirring constantly to prevent the ingredients from sticking.
Add the liquid pectin. Bring to a full rolling boil that cannot be stirred down with a spoon. Boil for 1 full minute, stirring constantly. Remove from heat.
Skim off any foam. Ladle jam into prepared jars, filling to within 1/8-inch of the top. Wipe jar rims and threads with a clean cloth or paper towel. Carefully place the flat lid on the glass rim; screw on the band. Place jars on elevated canner rack. Lower rack into canner. Water must cover jars by 1 to 2 inches; add more boiling water if needed. Cover and bring to a gentle boil. Process the jars for 10 minutes. Carefully remove the jars from the canner and sit them on a dishcloth on the counter. After jars cool, check seals by pressing the middle of the lid with your finger. If the lid springs back, the lid is not sealed and refrigeration is necessary.