1. Adjust oven rack to middle position and heat oven to 475°F. Combine tomato paste, 1 tablespoon oil, thyme, pepper flakes, 3/4 teaspoon salt, and 1/4 teaspoon pepper in large bowl. Toss tomatoes, garlic, and onion with tomato paste mixture until evenly coated. Place 4-inch-square of foil in center of wire rack set in rimmed baking sheet lined with aluminum foil. Place garlic cloves and onion rounds on foil and arrange tomatoes, cut side down, around garlic and onion.

2. Roast until vegetables are soft and tomato skins are well charred, 45 to 55 minutes. Remove baking sheet from oven and let cool 5 minutes. Transfer garlic and onion to food processor; pulse until finely chopped, about five 1-second pulses. Add tomatoes, vinegar, and remaining tablespoon oil to food processor. Pulse until broken down but still chunky, about five 1-second pulses. Using rubber spatula, scrape down bowl; season with salt, pepper, and sugar to taste. Continue to process sauce until slightly chunky, about five 1-second pulses. Stir in basil.

Makes 3 to 3 1/2 cups For 1 Pound of Pasta