Apex domains cannot have CNAME records.
Question and response
Question
dig fasttrackdns.com. NS
Answer
fasttrackdns.com. 5 NS NS3.fasttrackdns.com.
fasttrackdns.com. 5 NS NS1.fasttrackdns.com.
fasttrackdns.com. 5 NS NS2.fasttrackdns.com.
fasttrackdns.com. 5 NS NS4.fasttrackdns.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0