3 large red onions, halved, thinly sliced
 1 tablespoon olive oil
 1 tablespoon brown sugar
 4 (100g each) trim lamb leg steaks
 olive oil cooking spray
 4 small bread rolls, halved, toasted
 2 tablespoons low-fat hommus
 30g baby spinach leaves
 2 tomatoes, sliced
 225g can beetroot, drained