Preheat the oven to 375 F and marinate chicken with all the ingredients above for at least 30 min.
Peel a large onion & cut the bottom and top off. Pierce 2-3 soaked, wooden skewers through the top of the onion. Skewer marinated chicken thighs one by one. Roast in the oven for 20-25 min.
Shred cucumber, wrap in a paper towel and squeeze out all the water. Add the rest of the ingredients to make the tzatziki. Let it rest in the fridge.
In a mixing bowl, combine all the salad ingredients and place in the fridge.
Remove chicken from the oven and slice it. It should have some color but still be raw. Broil for 5-7 minutes until cooked through.