Extracting Content from HttpResponseMessage as HTML not string

There are a number of similar questions regarding extracting the content of an HttpResponseMessage, but most are looking for JSON or text.

I have an API in c# that calls another API which returns a Razor page. When I call the second API from Postman, it returns nicely formatted HTML that could be displayed in a browser right away. All I want my API to do (in this instance) is act as a middleman between the browser and the second API.

            var client = new HttpClient();

            const string uri = "Second API";

            var formData = new Dictionary<string, string>
            {
                // Data being sent to second API.
                {"path", "/somehwere/somefile.extension"}
            };
            var encodedFormData = new FormUrlEncodedContent(formData);
            
            var response = await client.PostAsync(uri, encodedFormData);

Now I have the response. If I do the following:

var test = await response.Content.ReadAsStringAsync();

The result is a string with various formatting characters such as "/n". This is not valid HTML and cannot be set as the src of an IFrame in the client browser (which is ultimately what I want to do).

I don't have an issue returning the data that I have extracted to the initial caller, my issue is with formatting.

How do I return valid HTML when I know that the second API is returning it (because Postman displays the html nicely, and because the browser can make the request and display it properly)?