Preheat the oven to 375 F.
Combine the spices, oil and lemon juice with the chicken. Mix well
If you have time, you can marinate the chicken for an hour or two. However, I find it has enough flavor that you can get away without marinating.
Lay the chicken in a baking dish 9x9in You can use any pan, just be aware that the more you pile on top of each other, the slower it cooks. I try to keep the chicken flat, or with 2 layers, never more than that.
Add the sliced onions on top
Tightly cover the pan with foil and cook for around 25-30 minutes (depending on how packed your pan is).
Using a sharp knife, thinly slice the chicken into shawarma-like strips and add it back into the sauce.
Serve warm with hummus, tehini, vegetables, cilantro, wraps, rice and any other toppings you like!