Begin by peeling the oranges, ensuring to remove as much of the white pith as possible. Segment oranges for easier processing.

Using an immersion blender, puree the orange pieces until smooth. Alternatively, use a stand blender in batches.

Add the sugar and optional spices to the orange puree, stirring gently to combine. Let it rest for about 10 minutes.

Cook the mixture over moderate heat, stirring often, for 20-30 minutes, until it thickens.

Pour the thickened jam into sterilized jars, leaving about 1/4 inch of headspace. Wipe down the rims of the jars.

Process jars in a water bath canner for 10 minutes to preserve. Let cool for 12-24 hours.