Apex domains cannot have CNAME records.
Question and response
Question
dig pantanodelburguillo.com. NS
Answer
pantanodelburguillo.com. 5 NS ns-833.awsdns-40.net.
pantanodelburguillo.com. 5 NS ns-1900.awsdns-45.co.uk.
pantanodelburguillo.com. 5 NS ns-611.awsdns-12.net.
pantanodelburguillo.com. 5 NS ns-1207.awsdns-22.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0