1. Drizzle vinegar over beets; refrigerate overnight.
2. Mix yogurt, mayonnaise, garlic, and dill in small bowl. Season to taste with salt, if necessary, and pepper to taste; set aside.
3. Squeeze lemon juice over apple slices. Place greens on platter or individual plates. Arrange apple slices and julienned beets over the greens; top with toasted pecans. Drizzle salad with dressing and serve. Or serve salad and pass dressing separately.