Apex domains cannot have CNAME records.
Question and response
Question
dig sisytec.net. NS
Answer
sisytec.net. 4 NS ns2.linode.com.
sisytec.net. 4 NS ns1.linode.com.
sisytec.net. 4 NS ns4.linode.com.
sisytec.net. 4 NS ns3.linode.com.
sisytec.net. 4 NS ns5.linode.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0