Apex domains cannot have CNAME records.
Question and response
Question
dig renweb.com. NS
Answer
renweb.com. 5 NS ns-1917.awsdns-47.co.uk.
renweb.com. 5 NS ns-931.awsdns-52.net.
renweb.com. 5 NS ns-162.awsdns-20.com.
renweb.com. 5 NS ns-1377.awsdns-44.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0