Soak the beans in water with a little baking soda for about eight hours.
Heat some olive oil in a stock pot. Then cut the onion into small pieces and toast it with the tomato paste.
Add the beans with the soaking water and cook until the beans are cooked (add water if necessary). This takes at least an hour and a half (important: do not add salt or broth to the beans before they are done, otherwise they will no longer be soft).
Clean the carrots and leeks, cut them into small pieces and add to the soup with the pureed tomatoes. Peel off the herbs or cut them into small pieces and sprinkle them into the soup. Simmer until the vegetables are cooked through.
Heat some olive oil in another pan. Dice the zucchini and sauté them separately. Pepper, salt and add to the soup that is ready with it.
The soup is creamy thanks to the beans, but can be diluted with a little broth. Then season accordingly.