In a small Mixing Bowl, whisk together the 3 tbsp aceite de oliva, 1 limón ralladoa y exprimido zest, 1 limón ralladoa y exprimido juice, minced 4 dientes de ajo picados, 1 tsp hojas frescas de tomillo, 1 tbsp romero fresco finamente picado, 2 tbsp perejil fresco finamente picado, 1 tsp sal kosher, 1 tsp sal kosher, and ½ tsp polvo de cebolla until combined.

Pat the 4 muslos de pollo con hueso y piel aproximadamente 2 ½ lb en total, secados con palmaditas completely dry with paper towels — this is the key to crispy skin. Place them in a shallow dish or Ziploc Bag and pour about two-thirds of the marinade over the 4 muslos de pollo con hueso y piel aproximadamente 2 ½ lb en total, secados con palmaditas. Reserve the remaining marinade for basting. Toss to coat well. Marinate at room temperature for 20–30 minutes, or refrigerate for up to 8 hours for deeper flavor.

Preheat your Oven to 400°F. Heat 1 tbsp of 3 tbsp aceite de oliva in a large oven-safe Cast Iron Skillet over medium-high heat until shimmering.

Remove the 4 muslos de pollo con hueso y piel aproximadamente 2 ½ lb en total, secados con palmaditas from the marinade and shake off any excess. Place the thighs skin-side DOWN in the hot Cast Iron Skillet. Sear undisturbed for 5–6 minutes until the skin is deep golden brown and releases easily from the pan. Do not move them — patience here gives you the crispiest skin.

Flip the 4 muslos de pollo con hueso y piel aproximadamente 2 ½ lb en total, secados con palmaditas skin-side UP. Brush the tops with the reserved marinade. Transfer the entire Cast Iron Skillet to the preheated Oven.

Roast for 25–28 minutes, until the internal temperature of the thickest part of the meat (not touching the bone) reads 165°F on an Meat Thermometer and the skin is deeply golden and crispy. Remove from the Oven and let the 4 muslos de pollo con hueso y piel aproximadamente 2 ½ lb en total, secados con palmaditas rest in the pan for 5 minutes.

Transfer the rested 4 muslos de pollo con hueso y piel aproximadamente 2 ½ lb en total, secados con palmaditas to a serving plate. Place the Cast Iron Skillet back on the Stovetop over medium heat. Pour in the ½ cup caldo de pollo bajo en sodio and scrape up all the browned bits from the bottom of the pan — that's where all the flavor lives. Let it simmer for 2–3 minutes until slightly reduced.

Remove the Cast Iron Skillet from heat and swirl in the 1 tbsp mantequilla sin sal until melted and the sauce looks glossy. Taste and adjust seasoning with 1 tsp sal kosher and 1 tsp sal kosher if needed. Spoon the pan sauce over the 4 muslos de pollo con hueso y piel aproximadamente 2 ½ lb en total, secados con palmaditas, garnish with fresh 2 tbsp perejil fresco finamente picado and 1 limón ralladoa y exprimido rounds, and serve immediately.