Apex domains cannot have CNAME records.
Question and response
Question
dig ecl.ntt.com. NS
Answer
ecl.ntt.com. 5 NS a1-20.akam.net.
ecl.ntt.com. 5 NS a6-64.akam.net.
ecl.ntt.com. 5 NS a7-65.akam.net.
ecl.ntt.com. 5 NS a12-65.akam.net.
ecl.ntt.com. 5 NS a13-66.akam.net.
ecl.ntt.com. 5 NS a20-67.akam.net.
Authority
The response has no authority records.
Additional
a1-20.akam.net. 2 A 193.108.91.20
a6-64.akam.net. 2 A 23.211.133.64
a7-65.akam.net. 2 A 23.61.199.65
a12-65.akam.net. 2 A 184.26.160.65
a13-66.akam.net. 2 A 2.22.230.66
a20-67.akam.net. 2 A 95.100.175.67
a1-20.akam.net. 2 AAAA 2600:1401:2:0:0:0:0:14
a6-64.akam.net. 2 AAAA 2600:1401:1:0:0:0:0:40
a7-65.akam.net. 2 AAAA 2600:1406:32:0:0:0:0:41
a12-65.akam.net. 2 AAAA 2600:1480:f000:0:0:0:0:41
a13-66.akam.net. 2 AAAA 2600:1480:800:0:0:0:0:42
a20-67.akam.net. 2 AAAA 2a02:26f0:67:0:0:0:0:43
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0