PUT Request with content type : text/html not working

Question

I am currently working in node, I need to understand put request method with access control allow headers, Below is my code

 import express from 'express'; 
    import cors from 'cors';
    const app = express();
    var corsOptions = {
       origin: '*',
       optionsSuccessStatus: 200, 
       allowedHeaders:['Content-Type: text/html'] 
    }
    app.put("/puttest", (req, res) =>  {
            console.log('in put');
            res.send({ 'message': ' Hello world !!! app is listening on port '})        
    });
   app.listen(3001, () => { 
        console.log('Listening to requests on 3001'); 
   });

It is not working why? can you please help me why it is not working when I provide any content-type: application/JSON or text/HTML?

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