To prepare Salmon Cakes: In a medium bowl, combine egg white, green onion, lemon juice, Dijon-style mustard, salt, and pepper. Add salmon and crushed crackers; mix well.
Form salmon mixture into four 3-inch patties, each about 1 inch thick. Lightly coat an unheated very large nonstick skillet with nonstick cooking spray. Preheat skillet over medium heat. Carefully add salmon patties. Cook about 8 minutes or until golden brown and heated through, turning once.
To prepare Caper Mayonnaise: In a small bowl, stir together mayonnaise, capers, lemon juice, and pepper. Stir milk to make drizzling consistency.
Top each salmon cake with about 1 tablespoon mayonnaise topping. If desired, garnish with lemon peel.