Final answer:
Lucio most likely chose the 'thinnest' piece of cake. This descriptive term fits the context of the question, while an artwork reference provides a visual representation of cake layers and frosting.
Step-by-step explanation:
Lucio chose the thinnest piece of cake on the dish if we are seeking to fill in the blank with a word that conveys Lucio's selection based on the width of cake pieces. In the context of describing the artwork in which cakes are depicted, Wayne Thiebaud's Boston Cremes can be referenced to give a better understanding of the cake's structure. Thiebaud's painting prominently features cakes with thick gooey frosting, and multiple layers defined by color and texture, creating a visual representation that resembles the description in the question.