For the marinade:
1/3 cup olive oil
1/4 cup tomato sauce
3 large cloves garlic, minced
2 tablespoons balsamic vinegar
2 tablespoons chopped fresh tarragon or 2 teaspoons dried tarragon
1/2 teaspoon salt
1/2 teaspoon cayenne pepper
1-1/4 pounds prawns, peeled and deveined
For the sauce:
1 cup butter (2 sticks), divided
1/3 cup dry white wine
1 tablespoon finely chopped shallots
1/2 cup heavy cream
1/2 cup chopped, seeded tomato
1 teaspoon Hungarian paprika
1. To make the marinade: In a small bowl combine all marinade ingredients. Place prawns in a resealable plastic bag in a shallow baking dish. Pour marinade over prawns; close bag. Marinate in refrigerator for 30 minutes, turning occasionally to distribute marinade.
2. Meanwhile, make sauce in last 10 minutes of marinating time: In a saucepan melt 1 tablespoon of the butter. Add wine and shallots; cook rapidly over high heat until liquid has almost evaporated. Add cream, tomato, and paprika; cook over medium heat until mixture is reduced and slightly thickened. Add remaining butter; stir until melted. Remove from heat and cover to keep warm.
3. Remove prawns from marinade; discard marinade.
4. Place prawns on cooking grate. Grill 6 to 8 minutes or until prawns turn pink and are opaque in thickest part (cut to test), turning once halfway through grilling time. Serve with warm sauce.