In a mixing bowl, combine the olive oil, garlic powder, dried oregano, salt, and black pepper. Add the chicken pieces and toss until well coated. Allow to marinate for at least 15 minutes to enhance the flavor.

In a separate bowl, mix the Greek yogurt, grated cucumber, minced garlic, chopped dill, lemon juice, and salt. Stir until well combined. Refrigerate until ready to use to allow the flavors to meld.

Heat a grill or grill pan over medium-high heat. Once hot, add the marinated chicken pieces. Grill for about 5-7 minutes, turning occasionally, until the chicken is cooked through and has nice grill marks.

Preheat your oven to 400°F (200°C). On a baking sheet, place the naan breads. Spread a generous amount of tzatziki sauce on each naan.

Top with grilled chicken pieces, sliced bell pepper, red onion, and cherry tomatoes. Sprinkle shredded mozzarella cheese on top.

Drizzle a little olive oil over the assembled naan pizzas to help them crisp up in the oven.

Bake in the preheated oven for 10-12 minutes, or until the cheese is melted and bubbly, and the edges of the naan are golden brown.

Remove from the oven and let cool for a minute. Slice into wedges and serve warm, garnished with extra tzatziki sauce if desired.