Wash and soak the butterbeans overnight, or a minimum of six hours.
Peel and roughly dice the onions.
Peel the garlic. If the cloves are too big, cut them in half.
Roughly dice the tomatoes, along with the seeds.
Wash the baby spinach and leave to dry.
Rinse and drain the butter beans.
In a pot over a medium/high heat, add the butterbeans, water, onions, garlic, tomatoes, rosemary, bay leaf and olive oil. Cover and bring to a boil. The moment it comes to a boil, reduce the heat and simmer for 30 minutes.
Check the stew after 20 minutes to ensure it has enough water. Continue cooking for another 10 minutes.
Once the butterbeans are soft to the touch, season with salt and pepper.
Cover and cook for another 5 minutes.
Once the butterbeans are tender and easily break, the stew is ready.
Stir in the baby spinach just before serving.
Serve hot with sourdough.