Apex domains cannot have CNAME records.
Question and response
Question
dig uhserver.com. NS
Answer
uhserver.com. 4 NS ns2.host.uol.com.br.
uhserver.com. 4 NS ns3.host.uol.com.br.
uhserver.com. 4 NS ns1.host.uol.com.br.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0