In a large nonstick pan, heat oil and then add the chicken, chopped onion, minced garlic, 1/4 cup lemon juice, cumin, oregano and enough salt and pepper to taste. Make sure chicken is well cooked and browned.
In a small bowl mix the mayo, lemon juice and garlic powder.
Heat flour tortillas by steaming in the microwave for 1 – 2 minute covered in a damp paper towel.
Assemble wrap by placing one tortilla on a piece of aluminum foil, then fill with chicken, garlic mayo spread, and then top with the optional toppings of tomato, onion, lettuce and/or tahini sauce. Wrap closed with foil and twist foil end.