Apex domains cannot have CNAME records.
Question and response
Question
dig hosting.smartspb.net. NS
Answer
hosting.smartspb.net. 5 NS ns5.smartspb.net.
hosting.smartspb.net. 5 NS ns2.smartspb.net.
Authority
The response has no authority records.
Additional
ns2.smartspb.net. 5 A 62.152.37.186
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0