Apex domains cannot have CNAME records.
Question and response
Question
dig sust-re.ae. NS
Answer
sust-re.ae. 3 NS nsa3.srv53.com.
sust-re.ae. 3 NS nsb3.srv53.org.
sust-re.ae. 3 NS nsd2.srv53.net.
sust-re.ae. 3 NS nsc3.srv53.net.
sust-re.ae. 3 NS nsa4.srv53.org.
sust-re.ae. 3 NS nsa2.srv53.net.
sust-re.ae. 3 NS nsb1.srv53.com.
sust-re.ae. 3 NS nsb2.srv53.net.
sust-re.ae. 3 NS nsc3.srv53.com.
sust-re.ae. 3 NS nsd2.srv53.org.
sust-re.ae. 3 NS nsd3.srv53.com.
sust-re.ae. 3 NS nsc3.srv53.org.
Authority
The response has no authority records.
Additional
nsa2.srv53.net. 4 A 178.32.247.0
nsb1.srv53.com. 3 A 135.181.9.147
nsb2.srv53.net. 4 A 135.181.9.151
nsa2.srv53.net. 4 AAAA 2001:41d0:203:dee4:178:32:247:0
nsb1.srv53.com. 3 AAAA 2a01:4f9:4a:530c:181:9:147:2
nsb2.srv53.net. 4 AAAA 2a01:4f9:4a:530c:181:9:151:2
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0