In a large bowl, mix the ollive oil, lemon juice, zest, garlic, paprika, onion powder, dried oregano, salt and pepper. Add the small chicken chunks to the marinate and toss to coat. Cover and store in fridge while you prep your toppings.
Remove the chicken and transfer to a hot skillet. Cook for 3-4 minutes per side or until cooked through (time varies with size of pieces).
When assembling/layering the toppings on the pita, make sure you season the tomato an onions with ADDITIONAL salt and pepper.