Unwrap the cheese and pat it dry with a paper towel. Using a sharp knife, slice the block of cheese into 8-12 slices and sprinkle with Italian seasoning.
Heat a large skillet with 1-2 teaspoons oil to medium-high heat. Place the Halloumi slices in the pan and cook for 1-2 minutes per side, until golden brown. (You may need to divide Halloumi into multiple batches depending on the size of your pan.)
Cut or tear the Halloumi slices into bite-size pieces and mix with bell peppers, cucumber, red onion and cilantro.
Whisk together Dijon mustard, vinegar, olive oil, sea salt and pepper. Toss vinaigrette with chopped salad and serve.