Heat a medium-size pot over medium heat and add the olive oil and butter.
Add the onion and carrots and sauté until onions are tender and translucent, about 6 minutes.
Add the tomatoes, salt, and pepper, and stir until fragrant, about 5 minutes.
Add the white beans and stock, bring to a boil and simmer partially covered for 20 minutes.
Puree the soup in the pot using an immersion blender or in batches using a regular blender. Taste for seasoning and serve.