Chicken Gyros

Peel cucumber and remove seeds.  Place cucumber in a food processor and process until smooth.  Drain well.

In a small bowl, stir together cucumber, dill weed, yogurt, sugar, garlic powder and celery salt.  Divide sauce in half.  Remove half of sauce and place in a plastic resealable bag.  Cover and refrigerate remaining half.

Add chicken to the plastic bag.  Shake to combine; refrigerate overnight.

Heat oil in a medium skillet over medium heat.  Add chicken and cook until cooked done (165 degrees) about 7 minutes.

To serve, evenly divide chicken between flat breads.  Top with tomatoes and onion slices, if desired.  Top with remaining cucumber sauce.