- 3 tablespoons unsalted butter
- 3/4 cup minced sweet onion, such as Vidalia
- 1 1/2 pounds tomatoes—peeled, seeded and chopped, with juices
- 1 teaspoon tomato paste
- 2 cups low-sodium chicken broth
- 1 basil sprig
- Freshly ground pepper
- 12 thin baguette slices, toasted
- 1/4 cup plus 2 tablespoons freshly grated Parmigiano-Reggiano cheese
- In a large saucepan, melt the butter. Add the onion and cook over moderate heat, stirring, until softened, about 5 minutes. Add the tomatoes and their juices, along with the tomato paste and cook, stirring, for 5 minutes. Add the broth and basil and season with salt and pepper. Simmer until the tomatoes are broken down, about 15 minutes. Discard the basil and puree the soup until smooth.
- Preheat the broiler and arrange the baguette toasts on a baking sheet. Sprinkle with the cheese and broil just until melted, about 30 seconds. Serve the soup with the cheese toasts.
The soup can be refrigerated overnight.