Remove the 1 ½ lb lomo de cerdo piel de plata recortada from the fridge 15–20 minutes before cooking to take the chill off. Pat it completely dry with paper towels — this is key for a good sear. If needed, trim any silver skin (the thin, shiny membrane) with a Knife.

In a Mixing Bowl, mix together the 1 tsp sal kosher, 1 tsp sal kosher, 1 tsp polvo de ajo, 1 tsp pimentón ahumado, 1 tsp tomillo seco, ½ tsp romero seco machacado, and ½ tsp polvo de cebolla. Rub the mixture all over the 1 ½ lb lomo de cerdo piel de plata recortada, pressing it into the surface on all sides.

Preheat your Oven to 425°F. Place an oven-safe Skillet (cast iron or stainless steel works best) over medium-high heat and add the 2 tbsp aceite de oliva. Heat until the oil is shimmering and just beginning to smoke.

Add the 1 ½ lb lomo de cerdo piel de plata recortada to the hot Skillet. Sear without moving it for 2–3 minutes until a deep golden-brown crust forms. Rotate to the next side and repeat, searing all 4 sides (about 8–10 minutes total). Add the 1 tbsp mantequilla sin sal in the last minute and tilt the pan to baste the 1 ½ lb lomo de cerdo piel de plata recortada.

Transfer the Skillet directly to the preheated Oven. Roast for 12–15 minutes, or until an instant-read Meat Thermometer inserted into the thickest part reads 145°F. Do not overcook — 1 ½ lb lomo de cerdo piel de plata recortada is very lean and dries out quickly.

Transfer the 1 ½ lb lomo de cerdo piel de plata recortada to a Cutting Board and tent loosely with Aluminum Foil. Let it rest for 5–10 minutes — this is non-negotiable for juicy results. The internal temperature will rise a few degrees as it rests.

While the 1 ½ lb lomo de cerdo piel de plata recortada rests, return the Skillet to medium heat (use Insulated Gloves — the handle is hot!). Add the 1 tsp polvo de ajo and sauté for 30 seconds until fragrant.

Pour in the ½ cup caldo de pollo and scrape up all the browned bits from the bottom of the pan with a Wooden Spoon — that's pure flavor. Stir in the 1 tbsp mostaza Dijon and let the sauce simmer for 2–3 minutes until slightly reduced.

Remove the Skillet from heat and swirl in the cold 1 tbsp mantequilla sin sal pieces one at a time until melted and the sauce is silky. Add fresh 1 tsp tomillo seco leaves if using. Taste and season with 1 tbsp mantequilla sin sal and 1 tsp sal kosher as needed.

Slice the rested 1 ½ lb lomo de cerdo piel de plata recortada into medallions about 1 inch thick. Arrange on a serving platter, drizzle generously with the pan sauce, and serve immediately.