Laravel Auth extend redirect if unauthorized

I’m authorizing my users using the Cognito Hosted UI from a custom guard. However the only way I can get the user redirected to the Hosted UI is by setting the headers myself, like so:

header("Location: https://{$this->domain}/login?scope=email+openid&$query");
exit;

However this is the wrong way to redirect within Laravel. If I attempt to use redirect()->away() then nothing happens, my protected page gets loaded regardless.

Here is my authenticate method, removed the rest of the code as it’s irrelevant:

// CognitoUserProvider.php

public function authenticate()
{
    redirect()->away("https://{$this->domain}/login?scope=email+openid&$query");
}

// AuthServiceProvider.php

public function boot()
{
    $this->registerPolicies();
    
    Auth::extend('cognito', static function () {
        return new CognitoUserProvider();
    });
}