In a small bowl combine shallot and 1 tablespoon vinegar. In a small saucepan simmer lentils in water to cover by 2 inches until just tender but not falling apart, 15 to 20 minutes, and drain well. Add hot lentils to shallot mixture and season with salt and pepper. Cool mixture, stirring occasionally. In a small heavy saucepan combine 1 1/2 cups water, bulgur, and salt and simmer, covered, until water is absorbed, 12 to 15 minutes. Transfer bulgur to a large bowl and cool completely, stirring occasionally. Add lentils to bulgur with celery, carrot, tarragon, remaining 2 tablespoons vinegar, oil, walnuts,and salt and pepper to taste and toss well. Salad may be make 1 day ahead and chilled, covered. Bring salad to room temperature before serving. Serves 4 as an entree or 6 as a side dish. Gourmet July 1994