How to Make It
Preheat oven to 325°F. Toss together tomatoes, crushed red pepper, 4 tablespoons of the oil, 2 tablespoons of the garlic, and 1 teaspoon of the salt in a 13- x 9-inch baking dish. Bake in preheated oven until tomatoes soften and release their juices, about 45 minutes. (You can do this step a few hours ahead of time. Let tomatoes stand at room temperature until ready to use.)
Bring a large pot of water and 1 tablespoon of the salt to a boil over high. Add spaghetti, and cook until al dente, 9 to 11 minutes. Drain spaghetti, reserving 1 cup cooking water.
Meanwhile, heat 2 tablespoons of the oil in a large skillet over medium. Add remaining 1 tablespoon garlic, and cook, stirring constantly, until just beginning to brown, about 1 minute. Add shrimp, and cook, stirring constantly, until shrimp begin to turn pink and are cooked through, about 2 minutes. Add reserved cooking water to shrimp mixture; reduce heat, and cook, stirring occasionally, 2 minutes. Stir in parsley.
Transfer drained pasta to a large serving bowl. Add shrimp mixture, tomatoes, basil, and remaining 2 tablespoons oil and 1/2 teaspoon salt, and gently toss. Serve immediately.