Begin by draining the soaked cannellini beans and placing them in a pot filled with fresh water. Bring to a boil over medium heat and let boil for 3 to 4 minutes. Drain again.

In a large stockpot, heat 2 to 3 tablespoons of olive oil over medium heat. Add minced onion and sauté for about 5 minutes until soft and translucent. Add chopped garlic and cook for an additional minute until fragrant.

Add prepared cannellini beans, followed by 1.5 liters of water or vegetable stock. Stir to combine, then bring to a rolling boil. Reduce heat to medium-low to simmer.

Cover the pot partly and let simmer for about 2 hours, stirring occasionally. If the soup is too thick, add a splash of water.

Once the beans are tender, stir in finely chopped celery and sliced carrots along with kosher salt and pepper. Simmer for 30 minutes.

Before serving, stir in lemon juice and zest, cooking for an additional 2 minutes. Taste and adjust seasoning, and serve hot.