Grilled Shrimp Cocktail

Sauce
12 large ripe plum tomatoes (about 3 pound)
1/2 cup extra-virgin olive oil
6 cloves garlic, lightly crushed
6 sprigs fresh thyme
3/4 teaspoon salt
1/4 cup ketchup
2 tablespoons prepared horseradish
1 tablespoon fresh lime juice
1 jalape?o chile, seeded and minced
1/4 teaspoon black pepper

Shrimp
8 (8-inch) bamboo skewers
48 large shrimp (about 2 1/2 pounds), peeled,
    deveined, tails left on
2 teaspoons chopped fresh thyme
1/2 teaspoon salt
1/2 teaspoon black pepper
Lettuce leaves

Sauce: Preheat oven to 275 degrees F. Line jellyroll pan with aluminum foil.

Bring pot of water to a boil. Working with half the tomatoes at a time, cook tomatoes in pot 30 seconds. Remove to colander; rinse with cold water to cool. Peel and core tomatoes; halve lengthwise; remove seeds. Set 4 largest halves aside. Place remaining halves, cut sides down, on prepared pan. Drizzle with oil; top with garlic, thyme and 1/2 teaspoon salt. Bake 2 1/2 hours, turning twice, until shriveled. Let cool. Pour off oil from pan and reserve (5 tablespoons). Reserve 3 garlic cloves, discarding remainder.

In blender, process roasted tomatoes, reserved tomatoes, 3 tablespoons reserved oil and 3 reserved garlic cloves, until smooth. Pour into bowl; add remaining salt, the ketchup, horseradish, lime juice, jalape?o and pepper. Cover; chill. (Can be made up to 3 days ahead.)

Shrimp: Soak skewers in cold water for 1/2 hour.

In bowl, mix shrimp, 2 tablespoons reserved oil, the thyme, salt and pepper. Thread shrimp on skewers. Heat ridged grill pan over medium-high heat. Grill shrimp 2 to 3 minutes per side, until cooked. Remove from skewers. Serve warm, at room temperature or slightly chilled, on lettuce with sauce.

Per serving: Makes 12 servings. Per serving: 164 calories, 13 g protein, 5 g carbohydrate, 10 g fat, 1 g fiber, 113 mg cholesterol, 439 mg sodium