Drain and rinse the chickpeas thoroughly, dry them, and season with black pepper and a squeeze of the lemon juice.
Dice the cucumber and tomatoes, slice the red onion thinly, and toss everything with the chickpeas, mint, remaining lemon juice and olive oil.
Pat the halloumi completely dry and slice it about half an inch thick.
Heat a dry nonstick or heavy pan over medium-high heat. Do not add oil — halloumi releases plenty of its own fat.
Sear the halloumi for 2 to 3 minutes per side, without moving it, until deeply golden.
Lay the hot halloumi over the dressed salad and serve immediately. Do not add salt at any stage.