Apex domains cannot have CNAME records.
Question and response
Question
dig calero.com. NS
Answer
calero.com. 5 NS ns-315.awsdns-39.com.
calero.com. 5 NS ns-1087.awsdns-07.org.
calero.com. 5 NS ns-649.awsdns-17.net.
calero.com. 5 NS ns-1974.awsdns-54.co.uk.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0