When employers search the talent pool on Cake (formerly CakeResume), they use keywords or criteria (e.g., front-end engineer, content marketing, project manager, etc.). The system then presents the resume(s) most relevant to the employer's input to ensure the best search results.
Therefore, there isn't a main resume displayed; only the one(s) that best match the employer's needs are shown.
If you prefer only one of your resumes to be searchable, you can set the other resumes to private.