1. You need 2 oven racks for this recipe. Place the first oven rack on the bottom shelf of the oven. Remove the second rack from the oven, we will need it later to secure the chicken tower in a standing position. Preheat oven to 400°F (200°C).
2. In a large bowl, combine chicken thighs and the marinade ingredients: Greek yogurt, lemon juice, finely grated fresh garlic, paprika, cumin, oregano, red pepper flakes, cinnamon, and salt. Mix well. Marinate for at least 30 minutes.


3. Cut onion in half. Place the onion halves next to each other cut side down on a large baking sheet. Insert a skewer into each onion half (I use 9.75-inch skewers). This will serve as the base for your chicken tower (you can use a vertical spit instead, if you have one).

4. Create the chicken tower by threading the marinated chicken pieces onto the skewers that are inserted into the onion halves, to form a vertical stack of chicken pieces.

5. Transfer the baking sheet with chicken tower to the preheated oven. To ensure the chicken tower doesn't fall during cooking, place another oven rack on the top shelf of your oven. Position the skewers between bars of the top rack to stabilize the tower.

6. Bake chicken shawarma in the hot oven for about 60 minutes, or until the internal temperature of the chicken reaches 165°F (74°C). Cooking time may vary depending on your oven.
7. While the chicken cooks, prepare pickled onions by combining sliced red onion with lemon juice, sumac, and some salt. Allow the onions to marinate for about 10 minutes, stirring a couple times.

8. Once the chicken stack is cooked, remove it from the oven. To transfer the chicken tower to a cutting board, gently slide a spatula under the bottom of the tower while holding the skewers with your hands for support. Carefully lift the chicken tower and place it on the cutting board.
9. To cut meat from the chicken tower, hold the skewers and use a sharp knife to make thin slices while gently moving it along the length of the skewers slicing off the edges. Serve shawarma chicken with marinated red onions and other toppings of your choice, store leftovers in an airtight container for up to 4 days.