Apex domains cannot have CNAME records.
Question and response
Question
dig primerelay.net. NS
Answer
primerelay.net. 5 NS ns2.primerelay.net.
primerelay.net. 5 NS ns1.primerelay.net.
Authority
The response has no authority records.
Additional
ns1.primerelay.net. 5 A 95.179.158.129
ns2.primerelay.net. 5 A 95.179.158.129
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0