1. Stir together the chickpeas, kidney beans, green beans, onions, peppadews, brine, 1 tablespoon lemon juice and the olive oil in a medium bowl. Season with salt and pepper.
2. Whisk together the yogurt and tahini until smooth. Season with salt and pepper.
3. Toss the lettuce with the remaining 1 tablespoon lemon juice and a pinch of salt. Divide the lettuce among 4 plates, top with the bean mixture and then the tuna. Drizzle with the yogurt dressing and sprinkle with the smoked paprika. Toss together just before eating.