Apex domains cannot have CNAME records.
Question and response
Question
dig impsat.com.co. NS
Answer
impsat.com.co. 5 NS juno.impsat.net.co.
impsat.com.co. 5 NS ns1.impsat.net.co.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0