On a plate, thoroughly combine walnuts and breadcrumbs; set aside. In a small bowl, combine jam and vinegar.
Season salmon with salt and pepper and brush both side with jam and vinegar mixture. Press walnut mixture evenly into both sides of salmon, finishing off the top sides with any excess mixture, pressing it in so it will hold.
Place salmon on a rimmed baking sheet; bake at 400F for about 15 minutes, or until salmon flakes easily with a fork.
TIP: When buying salmon, ask the fishmonger to skin it for you.