Spicy Beef Skewers

Ingredients

• 1 1/2 lb (675 g) flap steak or filet mignon, cut into large cubes
• 1/4 cup (60 ml) olive oil
• 3 tbsp (45 ml) tomato paste
• 2 tbsp (30 ml) lemon juice
• 1 tbsp ground sumac
• 1 tsp chili powder
• 1/2 tsp ground black pepper
• 1/2 tsp salt
• 1/4 tsp cayenne pepper, or more to taste
• 2 garlic cloves, chopped