Apex domains cannot have CNAME records.
Question and response
Question
dig instantgolf.org. NS
Answer
instantgolf.org. 5 NS ns-1389.awsdns-45.org.
instantgolf.org. 5 NS ns-1668.awsdns-16.co.uk.
instantgolf.org. 5 NS ns-1595.awsdns-07.co.uk.
instantgolf.org. 5 NS ns-1872.awsdns-42.co.uk.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0