1. Oil and heat grill.
2. Arrange salmon steaks on a baking sheet. Brush both sides of steaks with 2 teaspoons oil, then sprinkle steaks with salt and pepper.
3. Chop 1 bunch fresh tarragon; divide and press herb on both sides of salmon steaks. Grill steaks over medium-hot coals 4 to 5 minutes per side, until fish flakes easily with a fork.
4. Meanwhile, brush lemon slices with remaining 1 teaspoon oil; grill slices 1 to 2 minutes per side, until lightly charred.
5. To serve, divide remaining 2 bunches of tarragon among 6 serving plates. Divide and arrange grilled lemon slices on tarragon, then top each serving with a salmon steak. Serve with hot cooked couscous. Makes 6 servings.