How to Make It
In a mortar, combine 1 tablespoon oil, paprika, fennel seeds, and garlic; grind with a pestle until a smooth paste forms. Gently stir in parsley, tarragon, and 1/2 teaspoon salt. Let stand at least 20 minutes.
Lightly rub flesh side of fish with remaining 1 tablespoon oil; sprinkle with remaining 1/2 teaspoon salt. Spoon tarragon mixture over fish; refrigerate 1 hour.
Preheat charcoal or gas grill to medium heat.
After preheating the grill, turn the left burner off (leave the right burner on), or heap coals to one side of grill to create two temperature zones. Coat grill rack with cooking spray; place on grill. Place lemon halves, cut side down, on heated side of grill. Place fish, skin side down, on unheated side of grill. Cover and grill 10 minutes or until lemon is tender and well marked and fish flakes under gentle pressure. Remove fish from grill; discard skin. Cut fish into quarters. Serve lemon halves with fish.