What does the culinary term "Cardinal" indicate when cooking shellfish?

The term "Cardinal" in culinary contexts, particularly regarding shellfish, signifies the practice of cooking certain shellfish, which results in a red coloration. This is most notably relevant when preparing lobster or crab, where the shells naturally turn from a bluish or greenish hue to a vibrant red when cooked. This transformation not only enhances the visual appeal of the dish but also indicates that the shellfish is properly cooked.

The other options present interpretations that do not align with this specific culinary term. For instance, light seasoning would apply to various cooking techniques but is not a defining characteristic of "Cardinal." Similarly, while serving temperature may be relevant to certain dishes, it does not encapsulate what "Cardinal" specifies in the context of cooking shellfish. The use of tomato sauce, while it can sometimes accompany seafood dishes, does not relate directly to the definition of "Cardinal" either, which is specifically concerned with the color change associated with the cooking process itself. Therefore, the correct answer clearly reflects a crucial aspect of culinary terminology related to the presentation and preparation of shellfish.