Preheat your oven to 400°F (200°C). Wash and trim the beets, then wrap each beet in aluminum foil and roast for 45-60 minutes, or until tender. Let cool, peel, and slice into rounds.

In a small bowl, whisk together the fresh orange juice, olive oil, apple cider vinegar, Dijon mustard, and a pinch of salt until well combined.

In a large bowl, combine the mixed greens and red onion. Top with the roasted beet slices.

Drizzle the orange vinaigrette over the salad and gently toss to combine.

Sprinkle with chopped fresh mint leaves before serving.