Prepare all of your canning jars, lids, rings, and canning equipment* by washing in hot, soapy water and sterilizing if needed.
Heat the jars. Add water-filled jars (4 pints or 7-8 half-pints) to your water bath canner, and pour in enough water to cover the jars by 1-2”. Place the lid on and bring to a boil over high heat. Once a boil has been reached, turn off the heat and allow the jars to rest in the hot water while you prepare your cranberry sauce.
Before you get started: Place 5-6 metal spoons in your freezer so they will be ready when you need to test the cranberry sauce for consistency using the sheet test.
Boil sugar and water. Add the sugar and water to a large stainless steel stockpot and whisk well. Heat over high heat, bringing the mixture to a boil. Boil for 5 minutes, whisking often.
Add the cranberries. Pour in the cranberries and orange juice (if using) and return to a boil.
Simmer until set. Once a boil is reached, reduce the heat to medium-high and simmer (stirring often) until the berries are well broken down and the mixture “sheets” when tested with a cold spoon**, this will take approximately 15-25 minutes. Be sure to stir often to prevent scorching.
Add the orange zest and salt. Once the cranberries have mostly burst and the sauce passes the sheet test, stir in the orange zest (if using) and salt.
Fill the jars. Ladle the hot cranberry sauce into hot jars, leaving a ½” headspace from the top of the jar. Remove any air bubbles with a clean butter knife (if needed), then wipe the rims of the jars with a damp paper towel. Place a warm lid on top, then secure a canning ring just until fingertip tight. Transfer the filled jar to the water bath canner using a jar lifter. Repeat until all of the jars are filled or until the sauce is used up.
Process for 15 minutes. Once all of the jars are filled, place the lid on the canner and bring it to a rolling boil over high heat. Start the processing time only once a full boil is reached. Process for 15 minutes.
Cool down. Once the time is up, remove the lid and remove the canner from the heating element. Then allow the canner to cool for 5 minutes before removing the jars. Place the jars on a thick towel (or wire rack) and allow to rest in the same spot for 24 hours before transferring to storage.
Checking the seals and storage. After 24 hours, check the seals and remove the canning rings. Wipe down the jars and label them. Any jars that have not been sealed should be moved to the fridge to be eaten right away. Sealed jars store in a cool, dark place for at least 1 year as long as there are no signs of spoilage, broken seals, etc.