Apex domains cannot have CNAME records.
Question and response
Question
dig sureserver.com. NS
Answer
sureserver.com. 5 NS sgate4.sureserver.com.
sureserver.com. 5 NS sgate2.sureserver.com.
sureserver.com. 5 NS sgate1.sureserver.com.
sureserver.com. 5 NS sgate3.sureserver.com.
Authority
The response has no authority records.
Additional
sgate1.sureserver.com. 5 A 195.8.222.14
sgate2.sureserver.com. 5 A 195.42.142.79
sgate3.sureserver.com. 5 A 192.252.144.254
sgate4.sureserver.com. 5 A 116.251.204.79
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0