Step 1: Preheat oven to 400°F (200°C). Pour the canned San Marzano tomatoes (undrained) onto a large baking sheet. Drizzle with 1 tablespoon of olive oil and spread them out. Roast for 20-25 minutes, or until slightly caramelized and fragrant. This step significantly deepens the flavor of your creamy tomato soup.
Step 2: While tomatoes are roasting, heat the remaining 1 tablespoon of olive oil in a large heavy-bottomed pot or Dutch oven over medium heat. Add the chopped yellow onion and cook, stirring occasionally, until softened and translucent, about 8-10 minutes.
Step 3: Add the minced garlic to the pot and cook for another 1-2 minutes until fragrant, being careful not to burn it. This aromatic base is crucial for a delicious creamy tomato soup.
Step 4: Once roasted, carefully transfer the tomatoes from the baking sheet into the pot with the onions and garlic. Use a wooden spoon to scrape up any delicious caramelized bits from the baking sheet and add them to the pot.
Step 5: Pour in the vegetable or chicken broth. Add the chopped fresh basil, sugar (if using), salt, and black pepper. Bring the mixture to a simmer, then reduce heat to low, cover, and let it cook for at least 15 minutes to allow the flavors to meld. This slow simmer develops the rich taste of the creamy tomato soup.
Step 6: Remove the pot from the heat. Carefully use an immersion blender to purée the soup until it is completely smooth and creamy. Alternatively, transfer the soup in batches to a stand blender (be very careful with hot liquids) and blend until smooth. For an extra silky consistency, you can pass the puréed soup through a fine-mesh sieve.
Step 7: Return the puréed soup to the pot over low heat. Stir in the heavy cream. Heat gently until warmed through, but do not bring to a rolling boil after adding the cream, as it can curdle. Taste and adjust seasoning as needed.
Step 8: Ladle the hot creamy tomato soup into bowls. Garnish with additional fresh basil leaves, a swirl of cream, or a drizzle of olive oil, and serve immediately with your favorite accompaniments.