WstxLazyException error when using a variable as an HTML attribute in page blueprint

I am building a page blueprint that generates a URL in the backend and makes it available to the template. In the template I have the following:

<a href="<at:var at:name='myUrl'/>">My Text</a>

When I do this, the template is not rendered and an error is returned from the create draft service: [com.ctc.wstx.exc.WstxLazyException] Unexpected '<' in attribute value

I have tried to escape the '<' with '<' but it still doesn't work. When I use '<', the template is rendered with the link but the link doesn't have the href attribute.