Retrieving CGI Auth_User variable whith IIS Windows Authentication Enabled, ColdFusion 2018, and Microsoft Windows Server 2008 R2 Standard

I'm attempting to retrieve CGI variable Auth_User when a user has supplied their credentials after logging into their local computers using Active Directory.

I have ensured that Microsoft Authentication and Anonymous Authentication is Enabled at the Web Server Level and the Site Level in IIS.

I put the following code in the web.config which returned a 500 error.

<authentication mode="Windows" />
<identity impersonate="true" />
<authorization>
    <deny users="?" />
    <allow users="*" />
</authorization>

It states the Server_Protocol is HTTP/1.1, Server Software Miscrosoft-IIS/7.5.

Does anyone have any further suggestions?