Apex domains cannot have CNAME records.
Question and response
Question
dig mailermapfre.com. NS
Answer
mailermapfre.com. 3 NS esdns2.mapfre.net.
mailermapfre.com. 3 NS esdns3.mapfre.net.
mailermapfre.com. 3 NS esdns1.mapfre.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0