- 1/2 cup freshly squeezed yellow grapefruit juice (from 1 medium grapefruit)
- 1/2 cup packed cilantro leaves
- 2 medium serrano chiles, halved and seeded
- 4 medium garlic cloves, smashed
- Salt and freshly ground black pepper
- 1 1/2 cups freshly squeezed orange juice (from 4 medium oranges)
- 1 (3 to 4 pound) boneless pork loin
Mix all ingredients except 1/2 cup orange juice and pork until thoroughly combined. Add pork loin and turn to coat thoroughly. Place in refrigerator and let marinate at least 1 hour and up to 24 hours.
Heat oven to 450 degrees F and arrange rack in middle. Remove pork from refrigerator and let rest at room temperature while oven heats up. When oven is heated, remove pork from marinade, strain marinade and discard solids and reserve juices. Season pork well with salt and freshly ground black pepper. Place pork in a roasting pan and roast until skin is golden-brown and internal temperature registers 145 to 150 degrees F on an instant-read thermometer, about 50 to 55 minutes.
Remove pork to a cutting board and let rest at least 10 minutes before slicing.
Meanwhile, combine reserved marinade juices and remaining 1/2 cup orange juice in a small saucepan and bring to a boil over medium heat. Skim sauce let cook until mixture is reduced by 2/3, about 10 minutes. Taste and adjust seasoning, as necessary. When pork is ready, slice thinly and serve with orange sauce over top.