1. Warm oil in a large saucepan over medium-high heat. Add garlic and cook, stirring, until fragrant, about 1 minute. Stir in tomatoes with their juice, sugar, Italian seasoning and cayenne and bring just to a boil. Puree in batches and chill in refrigerator or over a larger bowl of ice water. Season with salt.
2. Ladle chilled soup into bowls. Top each portion with some shrimp and 1 tsp. pesto and serve.