Rinse the fresh cranberries under cold water and drain.
In a large bowl, combine the cranberries and baby spinach.
Add the sliced almonds and red onion to the bowl.
Prepare the orange by peeling and segmenting it, then add to the salad.
If using, crumble feta cheese over the top.
In a small bowl, whisk together olive oil and balsamic vinegar.
Drizzle the dressing over the salad.
Season with salt and pepper to taste.
Toss gently to combine all ingredients.
Serve immediately for best freshness.