Wash the oranges thoroughly, peel them, and separate the flesh from the peel.
Cut the orange flesh into bite-sized pieces and thinly slice the peel.
Place the orange flesh, peel, erythritol, and lemon juice into a pot.
Simmer over medium-low heat for about 30-40 minutes, stirring occasionally.
When the mixture thickens, transfer to a sterilized container and let it cool.