Apex domains cannot have CNAME records.
Question and response
Question
dig ratuobral.com. NS
Answer
ratuobral.com. 5 NS ns-333.awsdns-41.com.
ratuobral.com. 5 NS ns-1855.awsdns-39.co.uk.
ratuobral.com. 5 NS ns-80.awsdns-10.com.
ratuobral.com. 5 NS ns-926.awsdns-51.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0