01 - Set the oven temperature to 400°F.
02 - Individually wrap each beet in aluminum foil and arrange them on a baking sheet. Roast for 40 to 50 minutes, or until tender when pierced with a knife.
03 - Unwrap beets and allow to cool until manageable. Peel and slice into wedges or bite-sized cubes.
04 - Whisk together olive oil, balsamic vinegar, Dijon mustard, honey, salt, and black pepper in a small bowl until emulsified.
05 - In a large bowl, combine arugula, roasted beets, and sliced red onion. Drizzle dressing over and gently toss to combine.
06 - Transfer the salad to a serving platter and scatter crumbled feta cheese and toasted walnuts on top.
07 - Serve immediately for optimal freshness and flavor.