Bring a large pot of heavily salted water to a boil. Cook the gluten-free pasta according to package directions until al dente. Drain, rinse under cold water, and let cool.
Prepare the dressing by whisking together San-J Orange Sauce, olive oil, reserved mandarin juice, and a pinch of salt in a small bowl or jar.
In a large bowl, combine pasta, mandarin orange segments, cherry tomatoes, cucumber, and red onion.
Pour the dressing over the salad and toss gently to coat all the ingredients evenly.
Top with feta (if using) and fresh basil. Toss lightly again, taste, and add salt and pepper if desired, before serving.
Serve chilled or at room temperature, and garnish with a few extra basil leaves for a fresh finish.