I tried to follow steps mentioned in documentation below https://docs.aws.amazon.com/apigateway/latest/developerguide/apigateway-regional-api-custom-domain-create.html
created certificate as per ACM documentation for my region, and created a regional api gateway with custom domain name, still I am not able to map my api gateway to route53 a recordset.
As mentioned in docs we can not map regional custom domain name to a recordset from UI but it is also giving error below from CLI
An error occurred (InvalidChangeBatch) when calling the ChangeResourceRecordSets operation: Tried to create an alias that targets d-xxxxxxx.execute-api.ap-south-1.amazonaws.com., type A in zone ABCDEFGH, but the alias target name does not lie within the target zone