Now / Nuxt with serverMiddleware as functions

endpoint.js

import express from 'express'

const app = express()
app.use(express.json())

app.post('/endpoint', function(req, res) {
  try {
    // Do stuff
    res.status(200).end()
  } catch (e) {
    res.status(422).end()
  }
})

export default app

now.json

{
  "name": "example",
  "version": 2,
  "builds": [
    {
      "src": "api/endpoint.js",
      "use": "@now/node"
    },
    {
      "src": "frontend/nuxt.config.js",
      "use": "@nuxtjs/now-builder"
    }
  ],
  "routes": [
    {
      "src": "/endpoint",
      "dest": "/api/endpoint.js",
      "methods": ["POST", "OPTIONS"],
      "headers": {
        "cache-control": "s-maxage=31536000, max-age=0",
        "Access-Control-Allow-Methods": "POST",
        "Access-Control-Allow-Headers": "Content-Type"
      }
    }
  ]
}

nuxt.config.js

... 
serverMiddleware: process.env.NODE_ENV === 'production' ? [] : ['~/api/endpoint.js'],
...