Node API server with CORS disabled, AngularJS controllers with proxy and no proxy, and the ionic.project settings to allow proxy

app.js

var express = require('express')
var app = express()

app.get('/api/feed', function(req, res) {
  res.json({name: 'feed', items: ['first', 'second']})
})

var server = app.listen(3000, function () {

  var host = server.address().address
  var port = server.address().port

  console.log('Example app listening at http://%s:%s', host, port)

})

controllers.js

//Say we ran `ionic serve`
//This will access proxy, and pass along feed correctly
angular.module('starter.controllers', [])
.controller('DashCtrl', function($scope, $http) {
  $http.get('/api/feed').then(function(data) {
    console.log('data ' , data)
  })
})
//This will not access proxy, instead sending request straight across origin
//causing a failure to happen.
// XMLHttpRequest cannot load http://0.0.0.0:3000/api/feed. 
//No 'Access-Control-Allow-Origin' header is present on the requested resource. 
//Origin 'http://localhost:8100' is therefore not allowed access.
.controller('FeedCtrl', function($scope, $http) {
  $http.get('http://0.0.0.0:3000/api/feed').then(function(data) {
    console.log('data ' , data)
  })
})

ionic.project

{
  "name": "1test",
  "app_id": "",
  "proxies": [
    {
      "path": "/api",
      "options": "http://0.0.0.0:3000/api"
    }
  ]
}