.NET / C#

using System.Net.Http;
using System.Net.Http.Json;

var cpf    = "12345678909";
var apiKey = Environment.GetEnvironmentVariable("CPFHUB_API_KEY")!;

using var http = new HttpClient();
http.DefaultRequestHeaders.Add("x-api-key", apiKey);

var response = await http.GetFromJsonAsync<ApiResponse>(
    $"https://api.cpfhub.io/cpf/{cpf}"
);

Console.WriteLine(response!.Data.Name);       // "Fulano de Tal"
Console.WriteLine(response!.Data.BirthDate);  // "15/06/1990"
Console.WriteLine(response!.Data.Gender);     // "M"

record ApiResponse(CpfData Data);

record CpfData(
    string Cpf,
    string Name,
    string NameUpper,
    string Gender,
    string BirthDate,
    int Day,
    int Month,
    int Year
);

// Program.cs
builder.Services.AddHttpClient("cpfhub", client =>
{
    client.BaseAddress = new Uri("https://api.cpfhub.io/");
    client.DefaultRequestHeaders.Add("x-api-key",
        builder.Configuration["CPFHUB_API_KEY"]);
});

// CpfService.cs
public class CpfService(IHttpClientFactory factory)
{
    public async Task<CpfData?> LookupAsync(string cpf)
    {
        var client   = factory.CreateClient("cpfhub");
        var response = await client.GetFromJsonAsync<ApiResponse>($"cpf/{cpf}");
        return response?.Data;
    }
}