Drain soaked cannellini beans, place in a pot with fresh water, and boil for 3-4 minutes. Drain and set aside.

In a large pot, heat olive oil over medium heat. Add chopped onion and minced garlic, sauté until onion is soft and translucent, about 5 minutes.

Add the drained cannellini beans to the pot. Pour in vegetable stock and stir. Bring to a rolling boil.

Lower the heat, cover partially, and let simmer for about 2 hours, stirring occasionally.

Add diced celery and carrot, season with salt and pepper. Simmer for another 15-20 minutes.

Remove from heat and stir in lemon juice and zest before serving hot.