Apex domains cannot have CNAME records.
Question and response
Question
dig hsdomainkey.com. NS
Answer
hsdomainkey.com. 5 NS ns2.hsdomainkey.com.
hsdomainkey.com. 5 NS ns1.hsdomainkey.com.
Authority
The response has no authority records.
Additional
ns1.hsdomainkey.com. 5 A 74.122.193.133
ns2.hsdomainkey.com. 5 A 74.122.193.137
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0