Preheat your oven to 425°F (220°C) and line a large baking sheet with parchment paper for easy cleanup.

In a large bowl, toss the sliced chicken thighs and red onion with the olive oil, smoked paprika, cumin, coriander, garlic powder, salt, and pepper. Mix until the chicken is thoroughly coated in the spices.

Spread the marinated chicken and onions in a single, even layer on the prepared baking sheet. Bake for 20-25 minutes, tossing halfway through, until the chicken is cooked through and the edges are beautifully browned and crispy.

While the chicken roasts, prepare the garlic herb yogurt sauce. In a small bowl, whisk together the Greek yogurt, minced garlic, fresh dill, and lemon juice until smooth and creamy. Season with a pinch of salt to taste.

Remove the chicken from the oven and let it rest for 2 minutes. Serve the hot chicken and onions inside warm pita breads, generously drizzled with the homemade garlic herb yogurt sauce, and top with fresh lettuce or cucumbers if desired.