What link do I use to go back from a full page embed to the parent page?

I have a published doc that includes a full page embed of an external web page.

Users can click through from the home page of the doc to a subpage which is the full page embed of an external web page. That all works OK.

I want to put a “Back” button on the external web page that will take users back to the home page of the Coda doc where they started from. But if I simply link directly to that page, the header on the page is duplicated each time, like this:

Coda page embed link challenge

What link should I use instead, so that the user is returned to the original Coda doc home page, but without the header being duplicated?