In a bowl, combine the lemon zest and juice, tomato paste, ground coriander, cumin, smoked paprika, black pepper, turmeric, cayenne, cinnamon, Greek yogurt, olive oil, and salt. Whisk until smooth. Add the boneless, skinless chicken thighs, ensuring they're well coated in the marinade. Cover the bowl and let the chicken marinate for at least 15 minutes, allowing the flavors to infuse.

While the chicken marinates, wash and slice the red onions, mini cucumbers, and cherry tomatoes. Cut the onions into thin wedges for even roasting. The cucumber should be diced for a crisp texture, and tomatoes halved to preserve their juiciness. Set the chopped vegetables aside.

Preheat your oven to 400°F (200°C). Once heated, spread the marinated chicken thighs and sliced red onions evenly on a large sheet pan. Roast in the oven for 25-30 minutes or until the chicken is thoroughly cooked and golden brown on the outside.

While the chicken roasts, prepare the salad by combining diced cucumbers and halved tomatoes in a mixing bowl. Add chopped parsley, drizzle with olive oil, season with salt, and toss gently.

In a separate bowl, mix the remaining Greek yogurt with tahini and remaining chopped parsley. Stir until smooth and creamy.

Once roasted, remove the chicken and onions from the oven. Arrange on plates, add the salad alongside and drizzle with the tahini yogurt sauce. Serve warm with toasted pita.