Apex domains cannot have CNAME records.
Question and response
Question
dig sanluisobisporent.com. NS
Answer
sanluisobisporent.com. 5 NS ns-1520.awsdns-62.org.
sanluisobisporent.com. 5 NS ns-1770.awsdns-29.co.uk.
sanluisobisporent.com. 5 NS ns-505.awsdns-63.com.
sanluisobisporent.com. 5 NS ns-516.awsdns-00.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0