Apex domains cannot have CNAME records.
Question and response
Question
dig rmmservice.com. NS
Answer
rmmservice.com. 5 NS ns-1957.awsdns-52.co.uk.
rmmservice.com. 5 NS ns-479.awsdns-59.com.
rmmservice.com. 5 NS ns-657.awsdns-18.net.
rmmservice.com. 5 NS ns-1406.awsdns-47.org.
Authority
The response has no authority records.
Additional
ns-657.awsdns-18.net. 1 A 205.251.194.145
ns-1406.awsdns-47.org. 1 A 205.251.197.126
ns-1957.awsdns-52.co.uk. 1 A 205.251.199.165
ns-479.awsdns-59.com. 1 AAAA 2600:9000:5301:df00:0:0:0:1
ns-657.awsdns-18.net. 1 AAAA 2600:9000:5302:9100:0:0:0:1
ns-1406.awsdns-47.org. 1 AAAA 2600:9000:5305:7e00:0:0:0:1
ns-1957.awsdns-52.co.uk. 1 AAAA 2600:9000:5307:a500:0:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0