Apex domains cannot have CNAME records.
Question and response
Question
dig server5.grupofame.com. NS
Answer
server5.grupofame.com. 2 NS dns33098.dizinc.com.
server5.grupofame.com. 2 NS dns33099.dizinc.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0