Apex domains cannot have CNAME records.
Question and response
Question
dig graysmark.net. NS
Answer
graysmark.net. 5 NS ns1.graysmark.net.
graysmark.net. 5 NS ns2.graysmark.net.
graysmark.net. 5 NS ns3.graysmark.net.
Authority
The response has no authority records.
Additional
ns1.graysmark.net. 5 A 216.37.36.83
ns2.graysmark.net. 5 A 216.37.36.84
ns3.graysmark.net. 5 A 216.37.36.85
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0