Apex domains cannot have CNAME records.
Question and response
Question
dig ac.il. NS
Answer
ac.il. 5 NS nsb.ns.il.
ac.il. 5 NS nsa.ns.il.
ac.il. 5 NS ns1.ns.il.
ac.il. 5 NS ns4.ns.il.
ac.il. 5 NS ns3.ns.il.
ac.il. 5 NS lookup.iucc.ac.il.
ac.il. 5 NS ilns.ilan.net.il.
ac.il. 5 NS nse.ns.il.
Authority
The response has no authority records.
Additional
ns1.ns.il. 67170 A 194.146.106.122
ns3.ns.il. 91848 A 194.0.11.103
ns4.ns.il. 168485 A 204.61.216.134
nsa.ns.il. 133864 A 192.115.7.53
nsb.ns.il. 108508 A 192.115.7.60
nse.ns.il. 18701 A 192.115.4.235
ilns.ilan.net.il. 117416 A 128.139.35.5
lookup.iucc.ac.il. 171205 A 128.139.34.240
ns1.ns.il. 67170 AAAA 2001:67c:1010:31:0:0:0:53
ns3.ns.il. 91848 AAAA 2001:678:e:103:0:0:0:53
ns4.ns.il. 168485 AAAA 2001:500:14:6134:ad:0:0:1
nsa.ns.il. 133864 AAAA 2a01:4280:7:0:0:0:0:53
nsb.ns.il. 108508 AAAA 2a01:4280:7:0:0:0:0:60
lookup.iucc.ac.il. 171205 AAAA 2001:bf8:900:6:0:0:808b:22f0
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0