In a medium bowl, whisk together the orange juice, lime juice, olive oil, garlic, cumin, oregano, ancho chili powder, smoked paprika, salt, and black pepper.
¾ Cup Orange Juice, 6 Tbsp Lime Juice, 6 Tbsp Olive Oil, 12 Cloves Garlic , 2 Tbsp Cumin, 2 Tbsp Oregano, 1 Tbsp Ancho Chili Powder, 1 Tbsp Smoked Paprika, 1½ Tsp Salt, 1½ Tsp Black Pepper
Place the pork loin half sirloin roast in a large baking dish or container. Pour the marinade over the roast and turn to coat all sides.
4 lb Pork Loin Half Sirloin Roast
Cover and refrigerate for at least 4 hours. For the best flavor, marinate overnight or up to 24 hours, turning the roast once or twice during marinating.
Remove the roast from the marinade and reserve any remaining marinade in the refrigerator.
Preheat a grill to medium-high heat, approximately 375°F–425°F.
Sear the roast over direct heat for about 4 minutes per side.
Move the roast to indirect heat, close the lid, and continue cooking until the internal temperature reaches 145°F. For a 3–4 pound roast this will take approximately 2 hours, depending on your grill.
Remove the roast from the grill and rest for 10 minutes.
Shred or roughly chop the pork into bite-sized pieces.
Heat a cast iron skillet over medium-high heat and add the shredded pork.
Whisk together the cold water and cornstarch. Add the reserved marinade and cornstarch mixture to the skillet.
Reserved marinade, 1 Cup Cold Water, 1 Tbsp Cornstarch
Bring to a full boil and cook for at least 3 minutes, stirring occasionally, until the sauce thickens and the pork is piping hot.
Serve immediately.