Cumin Chicken Kebabs (Or Lamb Kebab)

Ingredients

• 500 g chicken breasts or 500 g chicken thighs, cubed
• 1 teaspoon cumin seeds or 1 teaspoon ground cumin
• 1 garlic cloves, crushed or 1/2 teaspoon minced garlic
• 2 teaspoons olive oil
• 1/2 teaspoon chili flakes or 1/4 teaspoon chili powder
• 1 teaspoon balsamic vinegar
• 4 teaspoons tomato puree or 4 teaspoons tomato sauce
• 2 red onions, sliced into thick wedges