Nuxt/Express API is returning in console but not browser - express

Question

I'm quite new to this whole backend business and I'm wondering if anyone can see where I'm going wrong. I've got an express server in my Nuxt app which is serving out an API. When I run the localhost:3000/api/salesforce/:id route - my vscode terminal generates a response - but it doesn't show up on the browser. Which in turn makes it inaccessible to Nuxt.
In my nuxt.config.js:
serverMiddleware: {
'/api': '~/api'
},
/api/index.js:
const express = require('express')
// Create express instance
const app = express()
// Require API routes
const users = require('./routes/users')
const test = require('./routes/test')
const salesforce = require('./routes/salesforce')
// Import API Routes
app.use(users)
app.use(test)
app.use(salesforce)
// Export express app
module.exports = app
// Start standalone server if directly running
if (require.main === module) {
const port = process.env.PORT || 3001
app.listen(port, () => {
// eslint-disable-next-line no-console
console.log(`API server listening on port ${port}`)
})
}
Then in /api/routes/salesforce.js:
const e = require('express')
const { Router } = require('express')
const router = Router()
const jsforce = require('jsforce');
// require the .env file for login
require('dotenv').config();
const { SF_USERNAME, SF_PASSWORD, SF_TOKEN, SF_LOGIN_URL } = process.env;
if (!(SF_USERNAME && SF_PASSWORD && SF_TOKEN && SF_LOGIN_URL)) {
console.error(
'Cannot start app: missing mandatory configuration. Check your .env file.'
);
process.exit(-1);
}
const conn = new jsforce.Connection({
loginUrl: SF_LOGIN_URL
});
conn.login(SF_USERNAME, SF_PASSWORD + SF_TOKEN, err => {
if (err) {
console.error(err);
process.exit(-1);
}
});
// get OPPORTUNITY specific
router.get('/salesforce/:id', function (req, res, next) {
const id = req.params.id
console.log(req.params.id)
const sfData = conn.query(`SELECT Id, Name, StageName FROM Opportunity WHERE Name = '` + id + `'`, (err, res)=>{
if(err){
console.log(err)
return "error";
} else {
console.log(res.records[0])
let sanitisedData = res.records[0]
return sanitisedData;
}
})
res.json(sfData.json)
})
If anyone can tell me where I'm going wrong that would be greatly appreciated, I'm kind of stuck here.