Preparation

• Thoroughly combine the peanut butter, chiles, 3 Tbs. of the oil, the lemon juice, 2 tsp. of the garlic, and 3/4 tsp. salt in a gallon-size zip-top bag. Lightly sprinkle the chicken thighs with salt, and then add to the marinade. Refrigerate for 1 hour, massaging every 15 minutes.
• Position a rack in the center of the oven, and heat the oven to 375°F. Heat the remaining 2 Tbs. of the oil in a large ovenproof skillet, preferably cast iron, on medium heat until shimmering. Add the onion, the remaining garlic, 2 Tbs. cilantro, and 1/2 tsp. salt, and cook over medium heat, stirring occasionally, until the onion softens and the garlic is fragrant, 4 to 5 minutes. Stir in the sweet potatoes. Cover the pan, and cook until the sweet potatoes just start to soften, stirring once, about 5 minutes. Turn off the heat.
• Remove the lid from the skillet, and add the tomatoes. Remove the chicken from the marinade, and place smooth side up over the tomatoes, spooning marinade on top of each. Scatter the peanuts over the chicken, and then transfer the skillet to the oven. Cook until the chicken reaches an internal temperature of 165°F, about 30 minutes.
• Heat the broiler on high, then cook until the top of the chicken and the peanuts turn light golden, 1 to 2 minutes, watching closely so that it doesn’t burn. Let the chicken rest for 10 minutes before serving, sprinkled with the remaining cilantro.