Apex domains cannot have CNAME records.
Question and response
Question
dig uk-ok.com. NS
Answer
uk-ok.com. 5 NS ns-495.awsdns-61.com.
uk-ok.com. 5 NS ns-779.awsdns-33.net.
uk-ok.com. 5 NS ns-797.awsdns-35.net.
uk-ok.com. 5 NS ns-1475.awsdns-56.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0