Prepare the Beans:

Drain the soaked beans.

Add to a pot half-filled with fresh water and bring to a boil. Cook for 3–4 minutes, then drain.

Stovetop Method:
3. In a medium pot, heat olive oil over medium-high heat. Sauté onion and garlic until soft and golden.
4. Add pre-boiled beans, 1.5 liters water (or 1L water + 500ml stock). Bring to a boil, reduce heat, and simmer partially covered for ~2 hours or until beans are soft.
5. Add celery, carrot, salt, and pepper. Simmer until soup thickens.
6. Stir in lemon juice and zest, cook 2 minutes more. Serve warm with extra lemon if desired.

Instant Pot/Pressure Cooker Method:
7. Using sauté function, cook onion and garlic in olive oil until golden.
8. Add beans, vegetables, 1.5 liters liquid (water + optional stock). Lock lid and cook on manual for 20 minutes.
9. Let pressure release naturally for 5–10 minutes, then quick release. Stir in lemon juice and zest before serving.

Slow Cooker Method:
10. Sauté onion and garlic in olive oil in a skillet, then transfer to slow cooker.
11. Add beans, vegetables, and 1.5 liters liquid (water + optional stock). Cook on low for 8 hours or high for 4 hours.
12. Stir in lemon juice and zest during the last 5 minutes of cooking.

Slow Cook Function on Instant Pot:
13. Sauté onion and garlic using sauté function.
14. Add remaining ingredients (except lemon) with 1.5 liters liquid.
15. Cook on slow cook mode—8 hours on normal or 4 hours on high. Finish with lemon juice and zest.