Apex domains cannot have CNAME records.
Question and response
Question
dig 24x7h.com. NS
Answer
24x7h.com. 5 NS ns1.sbdns.nl.
24x7h.com. 5 NS ns2.24x7h.com.
Authority
The response has no authority records.
Additional
ns2.24x7h.com. 5 A 134.19.182.186
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0