Into small bowl, with vegetable peeler, cut thin slices from each cucumber half up to seed portion. Stir in onion, vinegar, 1 teaspoon oil, salt and black pepper. Refrigerate until ready to serve.
Place oven rack 4 to 5 inches from broiler; preheat broiler. Coat both sides of salmon with remaining 4 teaspoons oil. In shallow baking dish, place salmon, skin side up, and broil 3 to 5 minutes or until skin is lightly browned.
With wide spatula, turn salmon. Pour lemon juice over salmon and sprinkle with lemon pepper seasoning, onion salt and garlic powder. Broil salmon 5 minutes.
In small bowl, mix sour cream and dill; spread evenly over salmon. Broil 3 to 4 minutes or until sour cream topping is lightly browned, salmon is almost opaque throughout and internal temperature reaches 145°. Slip spatula between salmon skin and fle