I’ve got a transform rule setup for my domain a.com that will concat some text to the pathname. For example, it would change a.com/some-page to a.com/some-text/some-page.
Is it possible for another domain b.com that CNAME’s to a.com to also be affected by this transform rule?
The only way to do this is in a setup where you have one zone with multiple custom hostnames, via SSL for SaaS.
This way you have one zone, main.com, which contains a custom hostname for a.com, b.com and so forth.
You could then create a Transform Rule (or any rule, for that matter) on main.com which will apply to all or a subset of those hosts served by this zone.