Preheat your oven to 400°F (200°C). Wrap whole beets in aluminum foil and roast for about 45-60 minutes, until fork-tender.
Once roasted, allow the beets to cool for a bit before peeling; the skin should come off easily with your fingers. Cut into wedges for an attractive presentation.
In a small bowl, whisk together honey, Dijon mustard, lemon juice, salt, and pepper until emulsified. Adjust sweetness and tanginess to your liking.
In a large bowl, combine spinach, beets, and drizzle with the dressing just before serving. Toss gently to coat.
Notes
This salad is best enjoyed fresh, but the components can be prepared ahead of time.