In medium bowl, combine mustard, canola oil, tarragon and garlic for marinade. Place salmon in marinade and gently toss until thoroughly coated. Place fish in resealable bag in refrigerator for at least 1 hour.
Heat grill to 375°F, when it's too hot to hold hand above coals for more than 5 seconds.

In 5-quart pot, bring 3 cups of water to a boil. Add lentils, garlic cloves and rosemary sprig. Cook lentils until just tender, about 30 minutes. Strain in colander.
In plastic bowl or cup with fitted lid, combine red onion, garlic, mustard, vinegar, canola oil, walnuts and pepper. Shake until thoroughly mixed and emulsified. Season with pepper.

In large bowl, toss lentils, carrots, celery and red onions together. Stir in enough vinaigrette, about 1/4 cup, to coat lentil mixture, and store rest in refrigerator for up to one week. Toss in fresh parsley and tarragon.
Spray grill rack lightly and cautiously with canola oil cooking spray, then carefully place salmon fillets on hot grill 2 inches apart. Cook on each side 3 to 4 minutes at diagonal angle to grill rack for professional-looking grill marks. Remove salmon from grill and serve over lentil salad. Garnish with lemon wedges, if desired. 

Nutritional Analysis per Serving: Calories, 420; Total Fat, 17 g; Saturated Fat, 1 g; Cholesterol, 60 mg; Sodium, 230 mg; Carbohydrates, 33 g; Fiber, 8 g; Protein, 34 g