In a medium saucepan, combine the fresh cranberries and orange juice over medium heat. Stir occasionally until the cranberries start to pop, about 5-7 minutes.
Reduce the heat to low and add in the maple syrup, cinnamon, nutmeg, and salt. Mix well and let it simmer for another 5 minutes until thickened slightly.
Stir in the orange zest and chopped walnuts (if using) and cook for an additional 2 minutes.
Remove from heat and allow the relish to cool down to room temperature. It will continue to thicken as it cools.
Once cooled, transfer to a serving bowl or an airtight container for storage. Keep refrigerated until ready to serve.
Notes
Can be made ahead of time and stored in the refrigerator.