Secondary domain redirects to a page within primary domain

[Redroot_Blades]

I have two domains registered with Shopify: redrootblades.com and redrootknives.com.

redrootblades.com is my primary domain and shop. Currently redrootknives.com just redirects to redrootblades.com.

What I want to do: 

I want to redirect "redrootknives.com" to the page www.redrootblades.com/pages/newsletter and also just show "redrootknives.com" or "redrootknives.com/pages/newsletter" as the url. 

So, users would type in "redrootknives.com" and they would be directed to redrootblades.com/pages/newsletter and ideally, the url would show redrootKNIVES not blades. 

Haven't found an answer on the community yet. It almost seems like I'd need to register redrootknives.com with a third party to do this redirect. When all my domains were with a third party, this type of redirection was easy. Is it really not possible within Shopify? 

Thanks,

Dustin