AUTH_USER from CGI is empty

I try to setup a very basic solution just to read the current logged in user from the CGI scope. I look for REMOTE_USER and AUTH_USER, but both are empty in Lucee dump of CGI scope.
I have a Apache 2.4 with mod_proxy config to route the requests to the Lucee server and back.
A direct call to port 8888 and dump cgi also shows me empty CGI scope for auth_user and remote_user
Does anybody here has a good example how to make the username of the current logged in user on the Laptop visible in Lucee?

that cgi variable only gets populated when you use webserver authentication

First, you need webserver authentification. And then, you need to forward the Headers to the endpoint, e.g.