Add glass jars to a pot of water. Boil for about one minute to sterilize the jars. Set the jars aside to cool and dry.
Rinse the citrus. Scrub the outside skin of the citrus with baking soda and/or salt. Let the citrus air-dry or pat dry with clean towels.
Slice the citrus thinly into roughly equal sizes. Make sure to remove any seeds to prevent bitterness.
Add the sliced citrus to a clean bowl with the sweetener and toss well to combine. Then, you can choose to dissolve the sugar using three different ways:
Microwave: Microwave the citrus sugar mixture in intervals (30 seconds - 1 minute), stirring in-between until all of the sugar is incorporated.
Stovetop: Add the marmalade mixture to a pot. Place it on a stove and cook until all of the sugar dissolves. (This process will cause the texture to slightly resemble jam, which is closer to how yuja tea is sold in stores. However, the taste will remain the same).
Letting the mixture sit: Add the marmalade mixture to the sterilized jars. Close the jars and let them sit at room temperature for 1-3 days until the sweetener has dissolved. You can use a clean spoon to stir the marmalade each day to help speed up the process.
Pour the prepared marmalade mixture into a jar, and store in the fridge. The citrus slices will continue to sweeten as it sits in the syrup. The marmalade will last for about a month.