In bowl combine all ingredients for caper vinaigrette. Allow to sit at room temperature for 30 minutes. Whisk once more to combine dressing. Adjust seasoning with salt and pepper if necessary.
Use a fork to flake the salmon into bite-sized pieces. In a large salad bowl combine spinach, walnuts and salmon.
Drizzle salad with a few tablespoons of caper vinaigrette. Toss to combine. Add more dressing if desired.
Sprinkle fresh cracked pepper over the top. Serve.
Notes
You can make the dressing ahead of time and refrigerate it. The olive oil will solidify in the the refrigerator but simply allow it to come to room temperature before using. Dress the salad immediately before serving. If you dress it too far in advance, the spinach will start to wilt. Nutrition information for estimation purposes only.