In a large mixing bowl combine the cumin, turmeric, coriander, garlic powder, cayenne pepper, paprika and cloves. Set aside the shawarma spice mix as you'll need it later.
Pat the chicken thighs dry and season generously with salt on both sides. Thinly slice chicken meat into small bite-sized strips.
Dump the chicken strips into the mixing bowl and toss in shawarma spices until the raw meat is fully coated.
Add the onions, lemon juice, lemon zest and olive oil. Toss again until the mixture is evenly coated. Cover and refrigerate for 3 hours or overnight to allow the chicken to marinate.
Before you're ready to eat, preheat the oven in your kitchen to 425 degrees. Take the chicken out of the fridge and let it sit at room temperature as the oven heats up.
Spread the marinated chicken with the onions in one layer on a large oiled baking sheet. Roast for 30 minutes, tossing the chicken shawarma after they've been in the oven for 15 minutes.
For a more browned, crispier chicken, move the pan to the top rack and broil very briefly for 1-2 minutes.
Remove roasted chicken from the oven and get ready to prepare a healthy shawarma plate or platter for a large group.