Put a frying pan over a medium heat and add the oil. When warm, add the onion, garlic and a pinch of salt (to draw out the moisture) and cook for a few minutes, until softened and starting to caramelise.
Add the beans, cumin, cayenne, tomatoes, half the lemon juice and 200ml water. Cook for 10–15 minutes over a medium to low heat until the tomatoes break down, and the liquid reduces to a reddish sauce.
Taste for seasoning and adjust the salt, lemon juice and cayenne accordingly.
While the beans are cooking, give the onions for the salad a head start by putting in a small bowl and covering with 1 tbsp lemon juice. Set aside.
For the tahini sauce, pound the garlic and a large pinch of salt to a paste using a pestle and mortar, then mix in the tahini. Add the lemon juice and a splash of water and mix until thin and drizzleable.
Hard-boil the eggs for 8 minutes. Remove from the heat immediately and run under cold water before peeling and slicing in half.
Add the remaining chopped salad ingredients to a bowl and mix together with the remaining lemon juice, a drizzle of oil and some salt.
To serve, put a large spoonful of salad on each plate, topped with a few lemony onions. Spoon on some beans, drizzle the tahini dressing over them, then top with parsley and a sprinkle of cayenne.
Nestle the egg halves on the plate and serve with flatbread for mopping.