Drain the beans from the water they've soaked in overnight.

Half fill a cooking pot with water and add the beans. Bring to a boil over high heat. Cook for 3-4 minutes and then drain beans in a strainer.

In a medium-sized cooking pot add the olive oil and heat over medium-high heat. Add the onion and garlic and cook until softened and golden in color.

Add the beans along with 1.5 liters of water (or 1 liter of water + 500 ml vegetable stock) and bring to a boil. Then reduce heat to medium-low and with the lid on partly open on the side, simmer for about 2 hours or until beans are completely soft and tender.

Add the celery and carrot and season with salt and pepper. Continue simmering, stirring occasionally until the soup gets nice and thick. Then add the lemon juice and zest and cook for 2 minutes more. Remove from heat and serve with freshly ground pepper on top and an extra squeeze of fresh lemon if you like.

Using the saute function, add the olive oil and cook the onion and garlic until softened and golden in color.

Add the remaining ingredients along with 1.5 liters of water (or 1 liter of water +500 ml vegetable stock) and close the lid. Cook on manual for 20 minutes. Let the pot sit for 5-10 minutes and then turn the valve to venting. Once it releases the steam open the lid. Finish off with the lemon juice + zest.

If using a slow cooker, take the time to separately saute the garlic and onion in olive oil until golden using a separate skillet. Add the sauteed ingredients in your slow cooker along with the remaining ingredients except for the lemon juice + zest, and 1.5 liters of water (or 1 liter of water +500 ml vegetable stock) and cook either on low for 8 hours or on high for 4 hours.

Add the lemon juice and zest and cook for 5 minutes more.

Using the saute function, add the olive oil and cook the onion and garlic until softened and golden in color.

Add the remaining ingredients along with 1.5 liters of water (or 1 liter of water +500 ml vegetable stock) except for the lemon juice + zest. Put the lid on and switch on the slow cooker function to normal, cook for 8 hours or for 4 hours on high.

Finish with the lemon juice + zest.