1. Make roasted red pepper tomato sauce (can be made up to 1 day ahead): Preheat oven to 375°F. Cut off and discard top quarter of garlic head and wrap remainder in foil. Arrange tomatoes, cut sides up, in a foil-lined 13- by 9- by 2-inch baking pan and sprinkle lightly with salt. Add whole bell pepper and garlic (in foil) to pan and roast vegetables in middle of oven 1 hour.
2. Transfer bell pepper to a bowl and cover bowl with plastic wrap, then let stand about 20 minutes. When cool enough to handle, peel pepper, discarding stem and seeds, and transfer to a food processor or blender along with tomatoes.
3. Unwrap garlic and squeeze roasted cloves from skin into food processor. Add remaining ingredients and salt and pepper to taste, then purée sauce until smooth. Makes 3/4 cup.
4. Make meatloaf: Preheat oven to 400°F. Cook onion and garlic in oil in a 12-inch nonstick skillet over moderate heat, stirring, until onion is softened, about 2 minutes. Add carrot and cook, stirring, until softened, about 3 minutes. Add mushrooms, 1/2 teaspoon salt, and 1/4 teaspoon pepper and cook, stirring occasionally, until liquid mushrooms give off is evaporated and they are very tender, 10 to 15 minutes. Stir in Worcestershire sauce, parsley, and 3 tablespoons ketchup, then transfer vegetables to a large bowl and cool.
5. Stir together bread crumbs and milk in a small bowl and let stand 5 minutes. Stir in egg and egg white, then add to vegetables. Add turkey and remaining 1/2 teaspoon salt and 1/4 teaspoon pepper to vegetable mixture and mix well with your hands. (Mixture will be very moist.)
6. Form into a 9- by 5-inch oval loaf in a lightly oiled 13- by 9- by 2-inch metal baking pan and brush meatloaf evenly with remaining 2 tablespoons ketchup. Bake in middle of oven until thermometer inserted into meatloaf registers 170°F, 50 to 55 minutes. Let meatloaf stand 5 minutes before serving.

Serves 6.

Nutritional Information: 1 serving meatloaf: 230 calories and 9 grams fat. Sauce: Each 2-tablespoon serving contains about 30 calories and 1 gram fat.