I got the answer from here: Proxy Preserve Host
Your application should be running in port, something like this 127.0.0.1:3000.
What you can do is to go to Websites > List of websites > Pick your website > Manage option. There you will find the vHost Conf section, there you should paste this:
extprocessor appname {
type proxy
address 127.0.0.1:your_app_port (3000 for this example)
maxConns 100
pcKeepAliveTimeout 60
initTimeout 60
retryTimeout 0
respBuffer 0
}
And the last step would be pasting the following in the Rewrite rules section
RewriteEngine On
RewriteRule ^(.*)$ HTTP://appname/$1 [P]
Best of luck!