$(document).ready(function () {

    var register = function() {
        var dataa = {
            Email: "password@host.com",
            Password: "password",
            ConfirmPassword: "password"
        };

        alert("test");

        $.ajax({
            type: 'POST',
            url: 'api/Account/Register',
            contentType: 'application/json; charset=utf-8',
            data: JSON.stringify(dataa)
        });
        return false;
    }

    $('#btnRegister').click(register);
});

[Authorize]
[RoutePrefix("api/Account")]
public class AccountController : ApiController
{
    [AllowAnonymous]
    [Route("Register")]
    public async Task<IHttpActionResult> Register(RegisterBindingModel model)
    {
        if (!ModelState.IsValid)
        {
            return BadRequest(ModelState);
        }

        var user = new ApplicationUser() { UserName = model.Email, Email = model.Email };

        IdentityResult result = await UserManager.CreateAsync(user, model.Password);

        if (!result.Succeeded)
        {
            return GetErrorResult(result);
        }

        return Ok();
    }
}