Sterilize jars in boiling water canner. and wash lids and tops with soapy water.
Coarsely chop the pears, then combine them with the sugar in a large pot and bring to a boil over medium heat, stirring to dissolve the sugar. Simmer, stirring frequently and lightly mash with a potato masher the pears soften, until the mixture thickens and is syrupy. This will take about 45 minutes, and you will see larger bubbles forming in the simmer.
Stir in the salt, lemon juice and cardamom, then simmer for 2 more minutes.
Ladle the hot preserves into hot jars leaving 1/4 inch headspace. Remove any air bubbles. Wipe the rims. Center the lids on the jars. Apply bands until the fit is just tight.
Process the jars in a boiling water bath canner for 10 minutes, adjusting for altitude. Turn off the heat and let the jars sit for 5 minutes then remove the jars and let cool in a draft-free spot overnight. Check the lids for seal after 24 hours – they should not flex up and down when the center is pressed. Store in a cool, dark place for up to one year.
Alternatively, if you don’t want to mess with the canning, you can skip the whole jar sterilizing and boiling water bath process -- just store in clean, air-tight jars in the refrigerator for up to a month.