Apex domains cannot have CNAME records.
Question and response
Question
dig postnice.org. NS
Answer
postnice.org. 2 NS ns-1808.awsdns-34.co.uk.
postnice.org. 2 NS ns-983.awsdns-58.net.
postnice.org. 2 NS ns-1112.awsdns-11.org.
postnice.org. 2 NS ns-1443.awsdns-52.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0