Enable CORS from a Node.JS Callback Function

I’m attempting to use Twilio Functions to handle token generation for my Twilio application. I previously was using a Node.js + Express Server to accomplish this, but I do not know how to figure out enable CORS in this type of environment.
My Client Code looks like this:

$('#new-twilio').click(function(){
        var toNum = this.value;
        if(token == undefined) {
            $.getJSON('https://my-twilio-function/endpoint').done(function(data){
                token = data.token;
                Twilio.Device.setup(token, {debug: true});
                Twilio.Device.ready(function(device){
                    Twilio.Device.connect({"PhoneNumber": toNum});  
                });
            }).fail(function(error){
                alert("Failure!");
                alert(JSON.stringify(error));
            });
        } else {
            Twilio.Device.connect({"PhoneNumber": toNum});
        }
    });

My function code looks like this:

exports.handler = function(context, event, callback) {
    const client = context.getTwilioClient();
    const ClientCapability = require('twilio').jwt.ClientCapability;
    const responseHeaders = {  
        "Access-Control-Allow-Origin": "*",
        "Access-Control-Allow-Methods": "GET, POST",
        "Access-Control-Allow-Headers": "content-type, accept",
        "Content-Type": "application/json"
    };
    let identity = "sampleIdentity";
    const capability = new ClientCapability({
      accountSid: context.ACCOUNT_SID,
      authToken: context.AUTH_TOKEN
    });
    capability.addScope(new ClientCapability.IncomingClientScope(identity));
    capability.addScope(new ClientCapability.OutgoingClientScope({
      applicationSid: context.TWILIO_TWIML_APP_SID
    }));
    console.log(capability.toJwt());
    callback(null, {headers: responseHeaders, identity: identity, token: capability.toJwt()});

};
Worth noting, the console.log proves that this function is returning the exact token I need, but I continue to get this error:

XMLHttpRequest cannot load https://my-twilio-function/endpoint. No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'http://localhost:8080' is therefore not allowed access.

Obviously, my twilio function is at a real URL. As much as I google, I cannot find how to allow access control to this type of node method.

Answer

This client code ended up working:

exports.handler = function(context, event, callback) {
  const client = context.getTwilioClient();
  const ClientCapability = require('twilio').jwt.ClientCapability;
  const response = new Twilio.Response();
  response.appendHeader('Access-Control-Allow-Origin', '*');
  response.appendHeader('Access-Control-Allow-Methods', 'GET,PUT,POST,DELETE');
  response.appendHeader('Access-Control-Allow-Headers', 'Content-Type');
  response.appendHeader('Content-Type', 'application/json');
  let identity = "sampleIdentity";
  const capability = new ClientCapability({
    accountSid: context.ACCOUNT_SID,
    authToken: context.AUTH_TOKEN
  });
  capability.addScope(new ClientCapability.IncomingClientScope(identity));
  capability.addScope(new ClientCapability.OutgoingClientScope({
    applicationSid: context.TWILIO_TWIML_APP_SID
  }));
  response.setBody({identity: identity, token: capability.toJwt()})
  console.log(capability.toJwt());
  callback(null, response);
};