Apex domains cannot have CNAME records.
Question and response
Question
dig isc.cl. NS
Answer
isc.cl. 5 NS ns2.isc.cl.
isc.cl. 5 NS secundario.nic.cl.
isc.cl. 5 NS ns1.isc.cl.
Authority
The response has no authority records.
Additional
ns1.isc.cl. 5 A 200.91.27.231
ns2.isc.cl. 5 A 200.27.240.165
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0