If preferred, peel pears. Cut pears lengthwise into quarters and remove cores and stem ends. Chop pears into chunks, bigger for chunky jam, smaller for a smooth batch.Combine pears, lemon zest, lemon juice, and sugar in a large bowl. Stir well to combine and cover. Let the mixture sit on the counter at least one hour, but preferably 8 hours, or overnight.After letting the mixture sit, stir well, scraping any sugar that may have collected on the bottom of the bowl. Place pear mixture in a heavy-bottomed non-reactive pan. Bring to a boil over medium high heat and cook for about 10 minutes, stirring occasionally to prevent the fruit from sticking to the bottom of the pan. Stir the fruit gently while cooking to reduce foaming.After about 10 minutes the fruit should be soft. Mash the pear chunks with a potato masher if you want smaller pieces, or mash completely for a smooth jam. Boil for 5-15 more minutes, stirring, until the jam either thickens to your liking or until it reaches 220 degrees on a candy thermometer.Once desired thickness has been achieved, remove the preserving pan from the heat and spoon mixture immediately into hot sterilized jars, leaving ¼-inch headspace for canning, or 1 inch if you plan to freeze. Look for any bubbles and use a plastic knife to pop them.At this point you can either cover jars with tight-fitting lids and store in the refrigerator for up to 3 months or in the freezer for up to 6 months, or you can process by following the next steps: Wipe rims of jars spotlessly clean and cover with sealing lids. Screw bands on finger-tight. Place jars on rack in boiling water bath canner, ensuring that tops of jars are completely submerged in hot water. Cover with a tight-fitting lid and process in a boiling water bath for 15 minutes.Remove jars from canner using jar-lifter tongs and gently set aside to cool on a kitchen towel in a draft-free place. Let rest for 24 hours, then check for a proper seal before storing.yield: Makes about 4 half pints