Apex domains cannot have CNAME records.
Question and response
Question
dig tan-re.co.tz. NS
Answer
tan-re.co.tz. 5 NS ns1.simbanet.co.tz.
tan-re.co.tz. 5 NS ns1.simbanetwork.com.
tan-re.co.tz. 5 NS dns1.simbanet.net.
Authority
The response has no authority records.
Additional
ns1.simbanet.co.tz. 5 A 196.45.36.100
ns1.simbanetwork.com. 5 A 116.203.121.168
dns1.simbanet.net. 5 A 41.221.41.100
ns1.simbanet.co.tz. 5 AAAA 2001:4258:0:0:0:0:53:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0