Preheat the oven to 180°C (350°F).
Scatter the chopped onion and minced garlic evenly across a baking dish (approximately 10 x 15 inches or 25 x 35 cm). Place the butter in the center of the dish and bake for 15 minutes, stirring if necessary to prevent any bits from browning excessively.
While the onion and garlic bake, prepare the Chicken Rub by mixing the paprika, dried thyme, garlic powder, onion powder, salt, and black pepper. Apply the rub generously to both sides of the chicken thighs.
Remove the baking dish from the oven and stir in the rice. Arrange the seasoned chicken on top of the rice.
Carefully pour the hot chicken broth and water around the chicken and rice mixture. Cover the dish tightly with foil and bake for 30 minutes.
After 30 minutes, remove the foil and lightly spray the chicken with oil, if desired, for a golden finish. Continue baking uncovered for an additional 20 minutes, or until the liquid is fully absorbed.
Allow the dish to rest for 5 minutes before removing the chicken. Fluff the rice with a fork and garnish with fresh parsley or thyme, if desired. Serve immediately and enjoy!