Apex domains cannot have CNAME records.
Question and response
Question
dig eicra.net. NS
Answer
eicra.net. 5 NS eicra.mars.orderbox-dns.com.
eicra.net. 5 NS eicra.mercury.orderbox-dns.com.
eicra.net. 5 NS eicra.venus.orderbox-dns.com.
eicra.net. 5 NS eicra.earth.orderbox-dns.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0