Preparation

• Position a rack in the center of the oven, and heat the oven to 400°F.
• Meanwhile, heat the oil in a large cast-iron or other oven-safe skillet over medium-high heat. Pat the chicken dry with paper towels, and season with 1 tsp. salt and 1/4 tsp. pepper. Add the chicken to the skillet skin side down, and cook until the fat is rendered and the skin is crisp and golden, 6 to 8 minutes (do not flip; the chicken will cook more later). Transfer the chicken to a large plate. Remove all but 1 Tbs. of fat from the pan.
• Add the onion to the skillet, and cook over medium heat, stirring occasionally, until softened, 2 to 3 minutes. Add the curry paste and garlic, and cook, stirring, until fragrant, about 30 seconds. Add the coconut milk, bell pepper, fish sauce, sugar, and 1/4 tsp. salt. Scrape up any brown bits at the bottom of the pan with a wooden spoon, and bring to a simmer. Season to taste with additional curry paste. Return the chicken to the pan skin side up, along with any accumulated juices from the plate.
• Transfer to the oven uncovered, and braise until a thermometer inserted in the thighs registers 165°F, 20 to 30 minutes.
• Transfer the thighs to a plate, leaving the sauce in the skillet. add the spinach to the skillet, and stir until wilted. Season to taste with juice from a couple of the lime wedges, salt, and pepper. Pour the sauce onto a serving platter or divide among plates, then nestle the chicken into the sauce and sprinkle with the cilantro. Serve with rice or noodles and the remaining lime wedges.