Like the figurative apple for the teacher, the tomato is a well-known food symbol representing a variety of cuisines. We drew on current scientific research and partnerships with classroom teachers to develop a case study activity consisting of four layers to teach concepts of plant biology and genetics to middle and high school students. The goal was to engage students in conversations about plants, their characteristics, functions, and genetic diversity that result in the variety of tomato shapes and sizes you find in the grocery store. Students were given a scenario in which both red and green tomato fruits are found in a local garden. They are taken through four layers that encourage them to consider possible environmental and biological factors that account for the differences in fruit color. Progressing from a review of basic anatomy to the design and execution of Punnett squares to an exploration of the other variations found across tomatoes, such as taste in a taste-testing exercise, students learn about the genetic variation of this ubiquitous fruit. Extension suggestions and samples of student worksheets are provided.