Apex domains cannot have CNAME records.
Question and response
Question
dig ielo.com. NS
Answer
ielo.com. 5 NS enel.ns.ielo.net.
ielo.com. 5 NS tata.ns.ielo.net.
ielo.com. 5 NS imin.ns.ielo.net.
Authority
The response has no authority records.
Additional
enel.ns.ielo.net. 5 A 45.10.224.134
imin.ns.ielo.net. 5 A 212.85.147.34
tata.ns.ielo.net. 5 A 188.121.227.9
enel.ns.ielo.net. 5 AAAA 2a02:2179:0:2:0:0:0:134
imin.ns.ielo.net. 5 AAAA 2a02:2178:1:2:0:0:0:3
tata.ns.ielo.net. 5 AAAA 2a02:2178:2:f:0:0:0:9
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0