Heat the oil in the base of a tagine or a large, heavy-based saucepan over a medium heat, stir in the onions and garlic and cook for 2–3 minutes until they begin to soften.
Add the runner beans and stir to coat well, then stir in the sugar, lemon juice, tomatoes and dill. Cover and cook gently for about 40 minutes until the beans are tender and the tomato sauce is fairly thick. Season to taste with salt and pepper, then garnish with the parsley. Serve with chunks of fresh crusty bread and bowl of thick, creamy yogurt, if liked.