Apex domains cannot have CNAME records.
Question and response
Question
dig amtex.com.co. NS
Answer
amtex.com.co. 5 NS ns30.domaincontrol.com.
amtex.com.co. 5 NS ns29.domaincontrol.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0