Gelatin Iceberg Ring With Tuna Salad

2 4 serving envelopes low-calorie lime-flavored gelatin ½ teaspoon salt 2 cup boiling water 1 ½ cup cold water 2 tablespoon vinegar 3 cup coarsely chopped Iceberg lettuce ¼ cup thinly sliced green onion

Tuna Salad

½ cup low-calorie mayonnaise 1 tablespoon lemon juice 2 tablespoon capers ¼ teaspoon salt Dash pepper 2 6.5 ounce cans tuna, drained and broken into pieces ¾ cup diced cumcumber