If you are using dried beans, soak them the night before and follow the instructions on the packet – this will add at least 1 hour onto the cooking time but will be much more economical. In this case, I would definitely double the recipe and freeze half!
Chop the onion very finely. Heat the oil in a heavy-based pan and add the onion. Cook and stir for 8 minutes or so until soft, and starting to brown.
Add the garlic, sumac and tomatoes. Blitz until smooth in a blender or hand-held stick blender. Add back to the pan with the remaining ingredients and 200 ml water.
Cover and cook over a medium-low heat for about an hour – stirring occasionally, until the starches from the beans are released and make the sauce thick.
Recipe Notes
cook once : eat twice
Freezes really well, so double the recipe and have one in the freezer for next time.