Heat the olive oil in a large saucepan or a flameproof casserole dish. Add the onion and courgettes and cook until the onion is soft and translucent.
Add the garlic, lemon zest, bay leaves and spices and stir for a couple of minutes to coat the vegetables. Pour in the tomatoes, then stir in the pinto beans and spinach cubes. Season with salt and pepper, then pour in 200ml of water.
Stir in some of the mint and parsley, reserving a few leaves for a garnish, then add a squeeze of lemon. Bring to the boil, then cover, turn the heat down to a simmer and leave to cook for 20 minutes.
Sprinkle in half the sumac and stir. Taste and adjust the sourness by adding more lemon juice to taste. Serve garnished with more herbs and sumac and maybe some flatbread on the side.