Heat a large nonstick pan over medium high heat. Cook each halloumi slab on all 4 sides, about 5 minutes. Set aside and allow to cool slightly; slice into cubes.
Whisk pomegranate vinegar, honey, harissa, olive oil and black pepper together in a bowl or a jar. Set aside.
Combine black beans, kidney beans, white beans, red onion, mint and coriander in a bowl; toss ingredients together with a spoon. Add cooked halloumi. Drizzle vinaigrette dressing over salad and toss again to coat.
Cover and allow to sit at room temperature at least 15 minutes.