Apex domains cannot have CNAME records.
Question and response
Question
dig srv53.org. NS
Answer
srv53.org. 5 NS NSD1.SRV53.NET.
srv53.org. 5 NS NSD1.SRV53.COM.
srv53.org. 5 NS NSC1.SRV53.ORG.
srv53.org. 5 NS NSB1.SRV53.NET.
srv53.org. 5 NS NSC1.SRV53.COM.
srv53.org. 5 NS NSD1.SRV53.ORG.
srv53.org. 5 NS NSA1.SRV53.COM.
srv53.org. 5 NS NSA1.SRV53.ORG.
srv53.org. 5 NS NSB1.SRV53.COM.
srv53.org. 5 NS NSC1.SRV53.NET.
srv53.org. 5 NS NSA1.SRV53.NET.
srv53.org. 5 NS NSB1.SRV53.ORG.
Authority
The response has no authority records.
Additional
nsa1.srv53.com. 5 A 178.32.247.7
nsa1.srv53.net. 5 A 5.39.10.94
nsa1.srv53.org. 5 A 178.32.247.3
nsb1.srv53.com. 5 A 135.181.9.147
nsb1.srv53.net. 5 A 135.181.9.148
nsb1.srv53.org. 5 A 135.181.9.149
nsc1.srv53.com. 5 A 78.27.225.73
nsc1.srv53.net. 5 A 78.27.225.72
nsc1.srv53.org. 5 A 78.27.225.71
nsd1.srv53.com. 5 A 89.184.64.99
nsd1.srv53.net. 5 A 89.184.64.68
nsd1.srv53.org. 5 A 89.184.64.93
nsa1.srv53.com. 5 AAAA 2001:41d0:203:dee4:178:32:247:7
nsa1.srv53.net. 5 AAAA 2001:41d0:203:dee4:5:39:10:94
nsa1.srv53.org. 5 AAAA 2001:41d0:203:dee4:178:32:247:3
nsb1.srv53.com. 5 AAAA 2a01:4f9:4a:530c:181:9:147:2
nsb1.srv53.net. 5 AAAA 2a01:4f9:4a:530c:181:9:148:2
nsb1.srv53.org. 5 AAAA 2a01:4f9:4a:530c:181:9:149:2
nsc1.srv53.com. 5 AAAA 2a02:2279:0:1201:78:27:225:73
nsc1.srv53.net. 5 AAAA 2a02:2279:0:1201:78:27:225:72
nsc1.srv53.org. 5 AAAA 2a02:2279:0:1201:78:27:225:71
nsd1.srv53.com. 5 AAAA 2a02:2278:70eb:298:89:184:64:99
nsd1.srv53.net. 5 AAAA 2a02:2278:70eb:298:89:184:64:68
nsd1.srv53.org. 5 AAAA 2a02:2278:70eb:298:89:184:64:93
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0