Apex domains cannot have CNAME records.
Question and response
Question
dig openenglish.com. NS
Answer
openenglish.com. 5 NS ns-638.awsdns-15.net.
openenglish.com. 5 NS ns-507.awsdns-63.com.
openenglish.com. 5 NS ns-1819.awsdns-35.co.uk.
openenglish.com. 5 NS ns-1244.awsdns-27.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0