Apex domains cannot have CNAME records.
Question and response
Question
dig tn. NS
Answer
tn. 5 NS ns2.ati.tn.
tn. 5 NS ns2.nic.fr.
tn. 5 NS ns-tn.afrinic.net.
tn. 5 NS rip.psg.com.
tn. 5 NS ns1.ati.tn.
tn. 5 NS pch.ati.tn.
Authority
The response has no authority records.
Additional
ns1.ati.tn. 162466 A 41.228.62.63
ns2.ati.tn. 162466 A 41.228.63.62
pch.ati.tn. 108855 A 204.61.216.94
rip.psg.com. 5 A 147.28.0.39
ns1.ati.tn. 162466 AAAA 2c0f:fab0:ffff:4:41:228:62:63
ns2.ati.tn. 162466 AAAA 2c0f:fab0:ffff:5:41:228:63:62
pch.ati.tn. 108855 AAAA 2001:500:14:6094:ad:0:0:1
rip.psg.com. 5 AAAA 2001:418:1:0:0:0:0:39
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0