Apex domains cannot have CNAME records.
Question and response
Question
dig tawk.to. NS
Answer
tawk.to. 2 NS amy.ns.cloudflare.com.
tawk.to. 2 NS seth.ns.cloudflare.com.
Authority
The response has no authority records.
Additional
amy.ns.cloudflare.com. 4 A 108.162.192.101
amy.ns.cloudflare.com. 4 A 172.64.32.101
amy.ns.cloudflare.com. 4 A 173.245.58.101
seth.ns.cloudflare.com. 4 A 108.162.193.142
seth.ns.cloudflare.com. 4 A 172.64.33.142
seth.ns.cloudflare.com. 4 A 173.245.59.142
amy.ns.cloudflare.com. 4 AAAA 2606:4700:50:0:0:0:adf5:3a65
amy.ns.cloudflare.com. 4 AAAA 2803:f800:50:0:0:0:6ca2:c065
amy.ns.cloudflare.com. 4 AAAA 2a06:98c1:50:0:0:0:ac40:2065
seth.ns.cloudflare.com. 4 AAAA 2606:4700:58:0:0:0:adf5:3b8e
seth.ns.cloudflare.com. 4 AAAA 2803:f800:50:0:0:0:6ca2:c18e
seth.ns.cloudflare.com. 4 AAAA 2a06:98c1:50:0:0:0:ac40:218e
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0