Step 1

In a heavy-bottomed soup pot, heat the olive oil, then add the red peppers, onion, and garlic. Cover and let cook over medium heat, stirring occasionally to break up the onion, until the peppers are soft and the onion is deeply caramelized—about 35 minutes.

Step 2

Uncover and add the tomato paste, diced tomatoes, and broth. Bring to a boil, then reduce heat to medium-low and simmer uncovered for 25 minutes, stirring occasionally.

Step 3

Stir in the vinegar, salt, and pepper. Blend until smooth with an immersion blender, or by transferring in batches to a blender and then returning to the pot. Adjust seasoning to taste with salt, vinegar, and sugar.

Step 4

To serve, ladle soup into bowls and sprinkle with more fresh black pepper. Garnish with fresh basil, and if using, one dollop of crème fraîche per bowl.