Step 1: Preheat the Oven

Preheat your oven to 375°F (190°C). Lightly grease a large oven-safe skillet or a 9×13-inch baking dish with cooking spray.

Step 2: Caramelize the Onions

1. Heat the olive oil in a large skillet over medium heat.
2. Add the sliced onions and cook, stirring frequently, for 15–20 minutes or until deeply golden and caramelized. If the onions start to stick, add a tablespoon of water or broth to deglaze the pan.
3. Remove the onions from the skillet and set aside.

Step 3: Sear the Chicken

1. Season the chicken breasts on both sides with garlic powder, paprika, salt, and black pepper.
2. In the same skillet used for the onions, add a bit more olive oil if needed. Sear the chicken over medium-high heat for 2–3 minutes per side, or until lightly browned (it doesn’t need to be fully cooked at this stage).
3. Remove the chicken and set aside.

Step 4: Prepare the Rice Mixture

1. In the skillet, combine the uncooked rice, beef broth, chicken broth, dried thyme, and half of the caramelized onions. Stir well to evenly distribute the ingredients.

Step 5: Assemble the Dish

1. Nestle the seared chicken breasts into the rice mixture in the skillet or transfer everything to a baking dish.
2. Top the chicken and rice with the remaining caramelized onions, spreading them evenly.

Step 6: Bake

1. Cover the skillet or baking dish tightly with aluminum foil. Bake in the preheated oven for 30–35 minutes, or until the chicken is cooked through (internal temperature of 165°F/74°C) and the rice is tender.

Step 7: Add the Cheese

1. Remove the foil and sprinkle the Gruyère and Parmesan cheeses evenly over the top.
2. Return to the oven and bake uncovered for an additional 10 minutes, or until the cheese is melted and bubbly. For a golden finish, broil for 2–3 minutes.

Step 8: Garnish and Serve

1. Remove the dish from the oven and let it rest for 5 minutes.
2. Garnish with fresh parsley and serve hot.