Spray a non-stick frying pan with low fat cooking spray. Cook the onion and garlic for 3-4 minutes over a low heat, until soft. Put them into a food processor with the chickpeas, parsley, coriander, cumin seeds, salt and flour and blend for 15-20 seconds to form a smooth, thick paste. (You could also use a hand-held stick blender). Form into 16 balls, about the size of testicles (ok, ping-pong balls). Chill for 10 minutes.
Preheat the oven to Gas Mark 4/180°C/fan oven 160°C. Mist a baking sheet with low fat cooking spray. Arrange the falafel balls on the baking sheet and bake for 15-20 minutes.
Arrange the lettuce, tomatoes and pepper strips on 4 serving plates. Make the dressing by mixing together the yogurt, cucumber and mint. Season. Serve the salads topped with the warm falafel, drizzled with the dressing.