Preheat the oven to 350 degrees F (175 degrees C).

Heat olive oil in a Dutch oven over medium-high heat. Season chicken thighs with 1 teaspoon salt, lemon-pepper seasoning, and 1/4 teaspoon garlic powder, rubbing into both sides. Add to the Dutch oven; cook until browned, about 4 minutes per side. Transfer chicken to a plate; set aside.

Melt butter in drippings in the Dutch oven. Add onion; cook and stir occasionally, 2 minutes.

Off heat, pour chicken stock and water into the Dutch oven, scraping the brown bits of food off the bottom of the Dutch oven with a wooden spoon. Stir in rice, lemon juice, remaining 1/2 teaspoon salt, remaining 1/4 teaspoon garlic powder, and black pepper. Place chicken on top of rice; cover Dutch oven with the lid.

Bake in the preheated oven for 30 minutes. Uncover; transfer chicken to a plate using tongs. Stir rice from bottom to top; return chicken to top of rice. Cook, uncovered, until all liquid is absorbed and rice is soft, about 15 minutes more.