- 1/4 cup butter
- 1 large leek – cut lengthwise, washed, trimmed, and thinly sliced
- 3 sprigs fresh rosemary, leaves stripped
- 2 teaspoons minced garlic
- 4 (16 ounce) cans diced tomatoes
- 1/4 teaspoon cayenne pepper
- 10 leaves basil, minced
- heavy whipping cream, or as needed
- salt and ground black pepper to taste
- Melt butter in a large saucepan over medium heat; cook and stir leek, rosemary, and garlic until leek is tender and translucent, about 15 minutes.
- Add diced tomatoes and cayenne pepper; bring to a simmer. Add minced basil; continue simmering until soup is reduced by half, about 1 hour.
- Remove half of the soup and puree in a blender until smooth. Return pureed soup to the saucepan. Stir in cream to desired consistency. Season to taste with salt and ground black pepper.