Apex domains cannot have CNAME records.
Question and response
Question
dig gigya-ugc.com. NS
Answer
gigya-ugc.com. 1 NS ns-2030.awsdns-61.co.uk.
gigya-ugc.com. 1 NS ns-717.awsdns-25.net.
gigya-ugc.com. 1 NS ns-429.awsdns-53.com.
gigya-ugc.com. 1 NS ns-1437.awsdns-51.org.
Authority
The response has no authority records.
Additional
ns-717.awsdns-25.net. 3 A 205.251.194.205
ns-1437.awsdns-51.org. 3 A 205.251.197.157
ns-2030.awsdns-61.co.uk. 3 A 205.251.199.238
ns-717.awsdns-25.net. 3 AAAA 2600:9000:5302:cd00:0:0:0:1
ns-1437.awsdns-51.org. 3 AAAA 2600:9000:5305:9d00:0:0:0:1
ns-2030.awsdns-61.co.uk. 3 AAAA 2600:9000:5307:ee00:0:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0