If using wooden skewers, soak them in water for at least 20 minutes to prevent burning.

In a large bowl, combine 2 tablespoons olive oil, cumin, smoked paprika, ground coriander, sumac, cayenne pepper, minced garlic, lemon juice, salt, and pepper. Mix well to form a marinade.

Add the halibut cubes to the marinade and gently toss to coat evenly. Cover and refrigerate for 15-20 minutes while preparing the relish.

Preheat a grill pan or barbecue to high heat. Place the whole bell peppers and red onion quarters directly on the grill, turning occasionally until charred on all sides, about 8-10 minutes.

Remove the charred vegetables and place in a bowl covered with cling film for 5 minutes to steam. Peel off the blackened skin from the peppers, remove seeds, and roughly chop. Finely chop the charred onion.

Combine the chopped peppers and onion with remaining 1 tablespoon olive oil, red wine vinegar, honey, and fresh parsley. Season with salt and pepper. Set the relish aside.

Thread the marinated halibut cubes onto skewers, leaving small gaps between each piece for even cooking.

Grill the halibut skewers over medium-high heat for 3-4 minutes per side, turning once, until the fish is opaque throughout and reaches an internal temperature of 63°C (145°F).

Transfer the skewers to a serving platter and let rest for 2 minutes. Serve immediately with the charred pepper relish spooned alongside and lemon wedges for squeezing.