Inside of my api gateway I have the following mapping template:

{
    "referring_domain" : "$context.domainName",
}

And inside of my lambda function I access this information in the following way:

const rDom = event.referring_domain;

However, when I log rDom I see \"xxxxxx.execute-api.us-east-1.amazonaws.com\" rather than the original domain that invoked the api domain.com.

Why is this?