Apex domains cannot have CNAME records.
Question and response
Question
dig vanity-sites.appiancloud.com. NS
Answer
vanity-sites.appiancloud.com. 5 NS ns-466.awsdns-58.com.
vanity-sites.appiancloud.com. 5 NS ns-1674.awsdns-17.co.uk.
vanity-sites.appiancloud.com. 5 NS ns-1481.awsdns-57.org.
vanity-sites.appiancloud.com. 5 NS ns-790.awsdns-34.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0