post method throws error,GET method working fine in API call in Angular

I getting below error in post method, GET method working fine also tried proxy configuration

Access to XMLHttpRequest at 'https://demotest/loginapi' from origin 'http://localhost:4200' has been blocked by CORS policy: Request header field content-type is not allowed by Access-Control-Allow-Headers in preflight response.

proxy.config.json

{
  "/loginapi": {
     "target": 'https://demotest'
     "secure": false,
     "changeOrigin": true,
     "logLevel": "info"
  }
}
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