Apex domains cannot have CNAME records.
Question and response
Question
dig sto.GBlNET.net. NS
Answer
sto.gblnet.net. 2 NS ns.GBlNET.net.
Authority
The response has no authority records.
Additional
ns.gblnet.net. 5 A 109.239.135.70
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0