To use a web server with filtering node as an intermediate server, you should create corresponding file of the virtual host (for example /etc/nginx/conf.d/example.com.conf).

Example of the virtual host file:

server {
        server_name  site.example.com;
        listen 80;

        location / {
                proxy_pass http://x.x.x.x;
                proxy_set_header        Host $http_host;
        }
}

where x.x.x.x is the address of destination server with the web application.

More information is available on the official page of the Nginx documentation.