DNS solution for someuser.com -> domain.com/some-user

Let's suppose there is a webpage where someone can create his own profile page.

His profile page is then available at

domain.com/some-user

Then, this user with profile domain.com/some-user, own his own domain

someuser.com

and he wants redirect from someuser.com -> domain.com/some-user

How can this be achieved?

I mean what DNS records must be set for someuser.com, and what web-server settings must be set on domain.com

Thanks