Apex domains cannot have CNAME records.
Question and response
Question
dig w1281.dnsclusterhost.com. NS
Answer
w1281.dnsclusterhost.com. 5 NS dns2.dnsclusterhost.com.
w1281.dnsclusterhost.com. 5 NS dns1.dnsclusterhost.com.
Authority
The response has no authority records.
Additional
dns1.dnsclusterhost.com. 4 A 64.40.12.250
dns2.dnsclusterhost.com. 4 A 64.40.12.251
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0