Make the candied walnuts (optional): Line a sheet pan with parchment paper. Add the brown sugar and butter to a small saucepan and heat over low, stirring until the sugar is dissolved and the butter is melted. Add the walnuts and continue to stir until well-coated. Spread the walnut mixture in a single layer on the prepared baking sheet, set aside, and allow to cool for at least 1 hour.
Make a batch of the apple cider vinaigrette and set aside.
Assemble the salad on a large serving platter or 4 salad plates. Add the greens, then top with apples and red onion. Sprinkle walnuts, cranberries, and pepitas. Finish by sprinkling the salad with feta cheese, then drizzle on the apple cider vinaigrette. Serve!
Notes
**Use 1 cup chopped walnuts for the salad if not using candied walnuts.