Preheat oven to 350°. Place cleaned beets in a small ovenproof dish, and add bay leaf, thyme and a tablespoon of water. Cover dish tightly with aluminum foil. Roast about 45 to 60 minutes, or until the beets are easily pierced by a knife. Place tangerine juice in a small saucepan and reduce to ¼ cup. Cool.
Peel and julienne cooled beets. Peel and finely julienne carrots (this can be done by hand or with a mandoline or serrated peeler.)
Whisk together yogurt, honey, tarragon, salt, pepper and reduced tangerine juice. Gently massage half the dressing into the kale shreds with your fingers. To massage, firmly rub the kale between your fingers until the kale softens and wilts, about 2 to 3 minutes. Let kale rest 30 minutes.
Toss remaining dressing with kale, beets, carrots and scallions and serve.