Sterilize five 1/2 pint canning jars by placing them in boiling hot water for 5 to 10 minutes.

In a large pot, combine the pineapple, jalapeño pepper, sugar, lemon juice, and butter. Cook on high, stirring often, until the mix boils.

Add the liquid fruit pectin, continuing to stir for 1 minutes while bringing the mix back to a boil. Then remove the pot from the heat source. Remove any foam.

Remove the jars from the water, then transfer the jam into the jars, leaving 1/4 inch space at the top of the jar. Run a knife around the inside of each jar to remove any bubbles. Clean the rims of any excess jam.

Seal the jars, then process them in a boiling water canner (approximately 10 minutes, but follow your canner's instructions). Then remove the jars and allow them to cool.

Preserve the jam in a cool dark location until ready to use.