Roughly chop the romaine lettuce and thinly slice the cucumber and red onion. Whisk vinegar, lemon juice, za’atar, salt, pepper, and minced garlic in a large bowl. Whisk in 3 tablespoons of oil.
Step 2
Slice the halloumi into ½ inch pieces. Heat a cast-iron skillet over high. Add the remaining 1 tablespoon of oil and swirl to coat. Working in batches, add cheese in a single layer and cook, flipping once, until browned, about 30 seconds per side.
Step 3
Add romaine, cucumber, and onion to the dressing and toss to combine. Divide among plates and top with cheese. Enjoy immediately.