My website's sftp server currently doesn't feature an .htaccess file. I have tried to add one so that when I type in the root URL, it doesn't automatically redirect to "index.php." Yet I always get a 500 error when this occurs, which leads me to believe either there is something wrong with the server or I am not creating a proper .htaccess file. Help?

Could you post a link to your site and the code you're using in your .htacess file?

The website is http://www.cmp.jobs/ (redirects to http://www.cmp.jobs/index.php)

I tried adding this code in the .htaccess file I created:
Options +FollowSymLinks
RewriteCond %{THE_REQUEST} ^.*/index.php
RewriteRule ^(.*)index.php$ http://www.cmp.jobs/$1 [R=301,L]

You could make it simpler try

Options +FollowSymLinks
RewriteEngine on
redirect 301 /index.php http://www.cmp.jobs/