Preheat oven to 375 degrees.
Place trimmed beets in roasting pan and pour water in to reach 1/2 inch depth. Cover the pan tightly with foil and bake for 1 hour. Remove from oven, carefully remove foil, and allow beets to cool.
While the beets are roasting, combine the cider vinegar and salt in a shallow bowl and stir until salt dissolves. Add sliced shallots, allowing the rings to separate, and pickle at room temperature for about 30-45 minutes.
Peel the cooled beets (I use gloves to keep from staining my hands). Cut each beet into 8-12 wedges.
Mix the olive oil with the marinating shallots to create a vinaigrette. Drizzle about 2 tablespoons of the oil and cider vinegar mix over the beets and toss to combine. Taste and season with salt and pepper (and maybe more vinegar, depending on your taste).
Toss the salad greens with some of the vinaigrette and place on one large plate or divide among individual salad plates. Tuck beet wedges among the salad leaves and garnish with shallots.
If desired, spoon small mounds of yogurt sauce around the salad or pass around so each person can choose the amount to use.