Apex domains cannot have CNAME records.
Question and response
Question
dig antel.com.UY. NS
Answer
antel.com.UY. 2 NS portal1.antel.com.uy.
antel.com.UY. 2 NS portal2.antel.com.uy.
Authority
The response has no authority records.
Additional
portal1.antel.com.uy. 2 A 200.40.1.129
portal2.antel.com.uy. 2 A 200.40.1.193
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0