**Preheat the oven**
Preheat your oven to 375°F (190°C). Lightly grease a 9x13-inch baking dish.
**Prepare the tzatziki sauce**
In a mixing bowl, combine the Greek yogurt, grated cucumber, olive oil, lemon juice, garlic, dill, and salt. Whisk until smooth and set aside.
**Assemble the dish**
Spread the uncooked rice evenly in the bottom of the baking dish. Pour the chicken broth over the rice, ensuring it is evenly distributed. Place the chicken breasts or thighs on top of the rice.
**Season the chicken**
Sprinkle the chicken with oregano, garlic powder, salt, and black pepper. If using, scatter the cherry tomatoes over the top.
**Top with tzatziki sauce**
Spread half of the prepared tzatziki sauce over the chicken. Reserve the remaining sauce for serving.
**Bake**
Cover the baking dish tightly with foil and bake for 40–45 minutes, or until the chicken is cooked through (internal temperature of 165°F/74°C) and the rice is tender.
**Garnish and serve**
Remove the dish from the oven and let it rest for 5 minutes. Garnish with fresh parsley and serve with the reserved tzatziki sauce on the side.