Apex domains cannot have CNAME records.
Question and response
Question
dig trc.es. NS
Answer
trc.es. 1 NS ns6.gnet.es.
trc.es. 1 NS ns4.gnet.es.
trc.es. 1 NS ns3.gnet.es.
trc.es. 1 NS ns5.gnet.es.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0