Apex domains cannot have CNAME records.
Question and response
Question
dig checkmyknowledge.org. NS
Answer
checkmyknowledge.org. 5 NS ns-1486.awsdns-57.org.
checkmyknowledge.org. 5 NS ns-1459.awsdns-54.org.
checkmyknowledge.org. 5 NS ns-727.awsdns-26.net.
checkmyknowledge.org. 5 NS ns-1868.awsdns-41.co.uk.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0