In small bowl, mix mayonnaise, sour cream, relish, catsup, mustard, sugar, lemon juice and vinegar. Beat with wire whisk til well blended. Remove core from lettuce; cut lettuce into 6 wedges. Put each wedge on salad plate. Cut each tomato into 6 wedges. Arrange 2 wedges on each plate. Spoon some dressing over each lettuce wedge. Pass remaining dressing around. Makes 6 servings.