MVC Redirect with custom headers

Hopefully this is a simple question for someone out there.

Basically upon receiving a request to my MVC controller, I want to:

1. Add an "Authorization" header to the response
2. Redirect to another application sitting on another domain
3. Read the "Authorization" header at this external site.

It appears the act of redirecting, strips out all my custom headers and redirects.

My question, how can I add a new header, AND perform a redirect, AND have that header show up in the headers for the receiving host [at the end of the redirect] to read?