Apex domains cannot have CNAME records.
Question and response
Question
dig electronicamartinez.es. NS
Answer
electronicamartinez.es. 5 NS ns2.electronicamartinez.es.
electronicamartinez.es. 5 NS ns.electronicamartinez.es.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0