Place pine nuts, honey, lemon juice, 1/4 cup olive oil, basil, garlic, and chile in a blender and process until the mixture is pureed. Spoon the sauce over the salmon, and turn to coat. Cover and refrigerate overnight or for at least 4 hours, turning twice.
Place bell peppers and watercress in a bowl. Toss with vinegar and 1 tablespoon olive oil. Cover and refrigerate while the salmon cooks.
Oil the grill rack and preheat the grill to medium-high. Remove the salmon from the marinade, reserving the marinade. Sprinkle the salmon with salt and pepper on both sides.
Place the salmon on the grill rack and grill until opaque throughout, 4 to 6 minutes on each side. Brush occasionally with reserved marinade. Garnish with bell pepper and watercress mixture before serving.