Options requests return 405 status

[ubudubu]

In blazor client app I want to make call to external API based on ntrada. I want to send DELETE request but httpClient sends preflight OPTIONS request. In response from API I get:

HTTP/1.1 405 Method Not Allowed
Connection: close
Date: Sun, 22 Mar 2020 10:00:31 GMT
Server: Kestrel
Content-Length: 0
Allow: DELETE

httpClient exception:

Access to fetch at 'http://localhost:5000/smth/e928eade-cd49-4bfa-b36a-5b0a7839b279' from origin 'https://localhost:4999' has been blocked by CORS policy: Method DELETE is not allowed by Access-Control-Allow-Methods in preflight response.

Shouldn't status code 200 be returned in this case?

My route config is:

      - upstream: /{id}
        method: DELETE
        use: downstream
        downstream: smth-service/smth/{id}?userId=@user_id
        auth: true
        bind:
          - userId:@user_id  

I tried to allow OPTIONS methods in that way:

      - upstream: /{id}
        methods:
            - DELETE
            - OPTIONS
        use: downstream
        downstream: smth-service/smth/{id}?userId=@user_id
        auth: true
        bind:
          - userId:@user_id  

but it occurred in exception:

System.Collections.Generic.KeyNotFoundException: 'The given key 'options' was not present in the dictionary.'

I also tried set forwardStatusCode to false but even then I got 405 instead of 200.