Apex domains cannot have CNAME records.
Question and response
Question
dig ntt.net. NS
Answer
ntt.net. 5 NS auth22.ns.gin.ntt.net.
ntt.net. 5 NS auth25.ns.gin.ntt.net.
ntt.net. 5 NS auth21.ns.gin.ntt.net.
ntt.net. 5 NS auth23.ns.gin.ntt.net.
ntt.net. 5 NS auth24.ns.gin.ntt.net.
Authority
The response has no authority records.
Additional
auth21.ns.gin.ntt.net. 5 A 129.250.35.230
auth22.ns.gin.ntt.net. 5 A 69.36.249.36
auth23.ns.gin.ntt.net. 5 A 129.250.31.22
auth24.ns.gin.ntt.net. 5 A 213.130.47.22
auth25.ns.gin.ntt.net. 5 A 116.51.22.181
auth21.ns.gin.ntt.net. 5 AAAA 2001:418:3ff:4:0:0:0:21
auth22.ns.gin.ntt.net. 5 AAAA 2001:1868:104:0:0:0:0:102
auth23.ns.gin.ntt.net. 5 AAAA 2001:418:0:700b:0:0:0:202
auth24.ns.gin.ntt.net. 5 AAAA 2001:728:0:7000:0:0:0:202
auth25.ns.gin.ntt.net. 5 AAAA 2001:218:4000:9:0:0:0:181
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0