Cut the halloumi into 6 slices.
Using a potato peeler to cut the courgette into long ribbons.
Cut the onion into thin wedges.
Mix the dressing: the olive oil, garlic and lemon juice, then set aside.
Oil a griddle pan, then grill the onion and courgette slices. When they are almost ready, brush them with some dressing and toss them in the pan for a few seconds, then transfer them to a plate.
Put the halloumi onto the griddle and brown them on both side. Again, brush them with the dressing and turn them over for a few seconds for the lemon and garlic to caramelize.
Meanwhile, scatter the rocket leaves onto a platter and arrange the courgette and onion slices on top.
Drizzle with the dressing.
When the cheese slices have nicely browned, transfer them on top of the salad and drizzle with the remaining dressing and scatter the lemon zest on top.
Serve at room temperature.