Step 1

Warm oil in a large pot over medium-high heat. Add onion, celery and carrots. Cook, stirring frequently, until vegetables have softened, about 5 minutes. Stir in tomato paste and beans. Pour in broth, season with salt and pepper, increase heat to high and bring to a boil. Reduce heat to medium and simmer, stirring often, until vegetables are tender, about 10 minutes.

Step 2

Remove soup from heat and allow to cool slightly. Working in batches, carefully puree soup in a blender until thick but still a bit chunky. Return soup to pot and bring to a simmer over medium heat. Season with salt and pepper. If soup is too thick, thin with additional broth. Serve hot, topped with pesto and croutons, if desired.