01 - Rinse cranberries thoroughly and pat dry.
02 - Combine cranberries, orange zest, orange juice, and chopped apple in a food processor; pulse until finely chopped but not pureed.
03 - Add granulated sugar, maple syrup (if using), and a pinch of salt to the processed fruit; pulse several times to combine.
04 - Transfer mixture to a bowl and fold in toasted walnuts gently.
05 - Sample and adjust sweetness as desired.
06 - Cover the relish and refrigerate for at least 1 hour to allow flavors to meld; serve chilled.