Apex domains cannot have CNAME records.
Question and response
Question
dig claro.net.co. NS
Answer
claro.net.co. 3 NS ns1.telmexla.net.co.
claro.net.co. 3 NS ns7.telmexla.net.co.
Authority
The response has no authority records.
Additional
ns1.telmexla.net.co. 3 A 190.157.8.71
ns7.telmexla.net.co. 3 A 190.157.8.71
ns1.telmexla.net.co. 3 AAAA 2800:480:ff78:c:0:0:0:1
ns7.telmexla.net.co. 3 AAAA 2800:480:ff78:c:0:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0