Apex domains cannot have CNAME records.
Question and response
Question
dig gdns.net. NS
Answer
gdns.net. 5 NS ns-1316.awsdns-36.org.
gdns.net. 5 NS ns-1796.awsdns-32.co.uk.
gdns.net. 5 NS ns-241.awsdns-30.com.
gdns.net. 5 NS ns-792.awsdns-35.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0