Apex domains cannot have CNAME records.
Question and response
Question
dig caballosgrancanaria.com. NS
Answer
caballosgrancanaria.com. 5 NS ns-1148.awsdns-15.org.
caballosgrancanaria.com. 5 NS ns-84.awsdns-10.com.
caballosgrancanaria.com. 5 NS ns-80.awsdns-10.com.
caballosgrancanaria.com. 5 NS ns-568.awsdns-07.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0