Whisk together MAGGI® Khaleeji Seasoning, pepper, minced garlic, lemon juice, and olive oil. Add the chicken cubes and let sit for 60 minutes.
When the chicken is well marinated, thread the chicken onto the skewers and heat the grill to medium-high heat or 200 degrees Celsius.
Oil the grill well and place the skewers on top, turning occasionally for about 10-15 minutes or until cooked through and well browned.
Remove from the grill and let rest for 5 minutes before serving.
Cut the cucumber in half lengthwise. Use a teaspoon to scrape out the watery seeds.
Coarsely grate the cucumber using a box grater, wrap in cheese cloth and squeeze to remove excess liquid.
To a bowl, mix the cucumber and the remaining ingredients to make the tzatziki.
Serve Souvlaki with pita bread on the side and garnish with sumac marinated sliced onions and the tzatziki.