multiple domain seo setting

I want to use 2 domain addresses on a single website.
Let’s name them as sites a and b.
Site a will be the main site.
When you enter the address of site b, site a will open, but the address of site b will be written in the browser. I don’t want to do a 301 redirect. Can I do this via cloudflare? If I can, I would like your help with the settings.
thanks a lot.

Hi @aturam96

I believe what you are looking for is a Host Header override Rule, this is only available for zones on the enterprise plan.