Prepare the pineapple by peeling, coring, and chopping it into small chunks. Pulse in a food processor to get about 3 cups of crushed pineapple.

In a large jam pot, combine the crushed pineapple and sugar. Bring to a rolling boil over high heat, stirring frequently. Cook for about 25-30 minutes.

Test for doneness using a cold plate from the freezer. If the jam mounds without running, it's ready. Continue boiling if necessary.

Ladle the hot jam into sterilized jars, leaving 1/4 inch headspace. Wipe the rims and place the lids on.

Process jars in a water bath canner covered with at least an inch of water for 10 minutes.

Cool the jars on a clean towel or wire rack and store in a cool, dark place.