CORS headers are set but still get an error

Hi guys I’m trying to send an ajax request to my meteor app and handle it some way. Here is my code.

import { WebApp } from 'meteor/webapp'
import ConnectRoute from 'connect-route'
import { Popups } from '../../imports/collections/popups/Popups'

const Fiber = Npm.require('fibers')

function onRoute (req, res, next) {
  res.setHeader('Access-Control-Allow-Origin', '*')
  res.setHeader('Access-Control-Allow-Headers', 'Origin, X-Requested-With, Content-Type, Accept')
  let rawPostBody = ''
  let postData = {}
  req.on('data', function (chunk) {
    console.log('on data')
    rawPostBody += chunk.toString()
  })
  req.on('end', function () {
    console.log('on end')
    postData = getPostData(rawPostBody)
    console.log('postData', postData)
    console.log('postData.event', postData.event)
    console.log('postData._id', postData._id)
    Fiber(() => {
      Meteor.call('updateAnalytics', postData, (error, result) => {
        if (error) {
          console.log('updateAnalytics error', error)
        }
        if (result) {

        }
      })
      console.log('res', res)
      res.writeHead(200)
      res.end()
    }).run()
  })
}

function getPostData (rawPostBody) {
  let postData = {}
  let pairs = rawPostBody.split('&')
  for (let i = 0; i < pairs.length; i++) {
    let kv = pairs[i].split('=')
    postData[kv[0]] = decodeURIComponent((kv[1] + '').replace(/\+/g, '%20'))
  }
  return postData
}

const middleware = ConnectRoute(function (router) {
  // 2uik9 is for webhooks requests
  router.post('/handlePopups', onRoute)
})

WebApp.connectHandlers.use(middleware)

Now when I do an ajax request from chrome console I get this error

XMLHttpRequest cannot load https://b2c.meteorapp.com/handlePopups. Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'http://stackoverflow.com' is therefore not allowed access.

Also nothing is logged in my server console.
But didn’t I set the headers? Am I doing it wrong?
Also note when I use a test http request service like Hurl.it it gets a response where it shows there are the headers

HEADERS

Access-Control-Allow-Headers: Origin, X-Requested-With, Content-Type, Accept
Access-Control-Allow-Origin: *
Content-Length: 0
Content-Type: text/plain; charset=utf-8
Date: Tue, 14 Mar 2017 10:39:59 GMT
Set-Cookie: galaxy-sticky=ESEFdEqGgiFCeS9P9-ras9; Path=/; HttpOnly

And my server console logs everything as it should.

So if my headers are all set what’s the problem here?