2 (1 pound) pork tenderloins, cut in 1/2 crosswise
Salt and freshly ground black pepper
1 1/2 cups apple cider
1/2 cup apple cider vinegar
1/4 cup maple syrup
Heat oven to 500 degrees F and arrange rack in the upper third.
Pat pork tenderloins dry with paper towels, brush with oil, and season well with salt and freshly ground black pepper. Heat a large frying pan over medium-high heat. Add 2 pieces of pork tenderloin and cook until brown on all sides, turning occasionally, about 4 minutes. Set pork aside on a baking sheet and repeat with remaining pieces.
Place pork in oven and cook until an instant-read thermometer inserted in the middle of the tenderloin registers 145 to 150 degrees F, about 15 minutes. Meanwhile, place pan over high heat, add cider and vinegar and stir, scraping up any browned bits. Cook until mixture is reduced by 2/3, about 8 minutes. Reduce heat to medium, stir in maple syrup and remove from heat until pork is cooked.
When pork is ready, remove to a cutting board to rest about 5 minutes. Warm sauce over medium-high heat, add pork and any accumulated juices and spoon sauce over meat to completely coat. When pork is warm, return pork to cutting board and slice thinly. Serve with pan sauce spooned over.