Baked Chicken Shawarma

Name: Baked Chicken Shawarma
Ingredients: 0.66666668653488 cup extra-virgin olive oil; 4 tablespoons finely minced fresh garlic; 2 medium lemons, juiced; 4 teaspoons smoked paprika; 4 teaspoons ground cumin; 1 tablespoon lemon zest; 2 teaspoons ground coriander; 2 teaspoons crushed red pepper flakes, or to taste; 2 teaspoons salt, or to taste; 1 teaspoon ground black pepper, or to taste; 1 teaspoon ground turmeric; 1 teaspoon ground cinnamon; 3 pounds boneless, skinless chicken thighs; 1 large onion, cut into 1/2-inch slices; 2 tablespoons chopped fresh parsley