Preheat the oven to 400°F (200°C). Pat the chicken dry with paper towels.
In a small bowl, combine garlic powder, smoked paprika, ground cumin, ground coriander, and salt; mix well. Season both sides of the chicken generously with about half of the spice blend and reserve the remaining half.
Heat the olive oil in a large heavy-duty cast iron skillet over medium-high heat. Sear the chicken thighs skin-side down until golden brown, about 4 minutes, then flip and sear the other side about 4 minutes. Transfer the seared chicken to a plate.
Add the diced onion and bell pepper to the same skillet and sauté for about 2 minutes until softened. Add the minced garlic and cook 30 seconds until fragrant.
Stir in the diced tomatoes, diced jalapeño, tomato paste, and the remaining spice blend. Sauté 2–3 minutes until the tomatoes begin to soften and the mixture is fragrant.
Add the rice, frozen peas, and about half of the chopped cilantro to the pan and stir to combine, then pour in the water and bring to a simmer.
Return the seared chicken to the pan, placing pieces on top of the rice. Cover the skillet tightly with foil and transfer to the oven; bake 30 minutes or until the chicken is cooked through and the rice is tender and liquid is absorbed. Alternatively, cook covered on the stovetop over the lowest heat until done.
Optional: For crispier skin, place the cooked skillet under the broiler 4–5 minutes until the chicken skin is crisp.
Remove the chicken, fluff the rice with a fork, garnish with remaining chopped cilantro, and serve.