How to Make It
Preheat the oven to 425°. In a large, deep ovenproof skillet, whisk 1 1/4 cups of the vinegar with the water, sugar and 1 tablespoon of salt. Add the beets, thyme, garlic and bay leaf. Cover the skillet and roast the beets for about 45 minutes, until tender, turning them halfway through. Remove the beets from the skillet and let cool completely, then peel and cut into wedges; discard the cooking liquid.
In a medium bowl, whisk the yogurt with the shallot and the remaining 3 tablespoons of vinegar. Season the dressing with salt and pepper.
Arrange the lettuce on a platter and top with the beets. Drizzle with half of the dressing and garnish with cilantro leaves and dill sprigs. Serve right away, passing the remaining dressing at the table.