Cook the beets: Preheat the oven to 400°F (200°C). Wrap the unpeeled beetroots in aluminium foil and place them on a baking sheet. Roast for about 1 hour, or until the beets are tender when pierced with a fork.
Once the beets are cool enough to handle, remove them from the foil and let them cool completely. Once cool, peel the beets and discard the skins.
Using a large-hole grater, grate the beets into a medium bowl.
In a separate bowl, combine the yoghurt, crushed garlic, and salt. Whisk until well combined.
Pour the yoghurt dressing over the grated beets and gently toss to combine.
Refrigerate the salad for at least 30 minutes to allow the flavours to meld. Serve chilled, garnished with chopped walnuts, fresh dill, or a drizzle of olive oil, if desired.