This Grilled Grouper Sandwich is a culinary masterpiece. The herbal intensity of rosemary bathes the fish in smoke-kissed flames that mingle with Cajun spice and a zesty lemon vinaigrette to create “perfection on a bun.” The crisp bun, crunchy lettuce, vinegary pickled red onion, and creamy rémoulade all combine to redefine the term “fish sandwich”…