Spicy Fish Kebobs

Ingredients

• ¼ cup olive oil
• 1 lemon, juiced
• 6 cloves garlic
• 2 tablespoons harissa (red pepper paste)
• 1 teaspoon ground cumin
• ½ teaspoon freshly ground black pepper
• salt to taste
• 1 ⅓ pounds 1-inch-thick tuna, skin removed and flesh cut into 30 cubes
• 1 red bell pepper - seeds and ribs removed and pepper cut into 15 squares
• 1 yellow bell pepper - seeds and ribs removed and pepper cut into 15 squares
• 1 large red onion, cut into wedges and layers separated
• 6 skewers