Prepare the Beans

1. Drain soaked beans.
2. Place beans in a pot and half fill with water.
3. Bring to a boil over high heat and cook for 3–4 minutes.
4. Drain and set aside.

Stovetop Method

1. In a medium pot, heat olive oil over medium-high heat.
2. Add onion and garlic and sauté until soft and golden.
3. Add beans and 1.5 liters water (or 1 liter water + 500 ml vegetable stock).
4. Bring to a boil, then reduce heat to medium-low. Simmer partially covered for about 2 hours, or until beans are very tender.
5. Add carrot and celery. Season with salt and pepper.
6. Continue simmering until soup thickens, stirring occasionally.
7. Stir in lemon zest and juice. Cook 2 minutes more. Serve with extra black pepper and lemon if desired.

Instant Pot / Pressure Cooker

1. Using sauté function, cook olive oil, onion, and garlic until softened.
2. Add beans, carrot, celery, salt, pepper, and water (or water + stock).
3. Cook on Manual/Pressure for 20 minutes.
4. Let rest 5–10 minutes, then release pressure.
5. Stir in lemon zest and juice before serving.

Slow Cooker

1. Sauté onion and garlic separately in olive oil until golden.
2. Add to slow cooker with beans, carrot, celery, salt, pepper, and water (or water + stock), excluding lemon.
3. Cook on Low for 8 hours or High for 4 hours.
4. Stir in lemon zest and juice during the last 5 minutes.