Beer-Marinated Pork Tenderloin with Red Cabbage

Place pork in a large resealable plastic bag. Whisk lager, soy sauce, brown sugar, and 1 tablespoon vinegar in a small bowl; pour into bag with pork and seal. Chill, turning occasionally, for at least 4 and up to 24 hours. Preheat oven to 400 °F. Heat oil in a large ovenproof skillet over medium-high heat. Remove pork from marinade, allowing any excess to drip off (reserve marinade). Cook pork, turning, until browned on all sides, 8-10 minutes. Transfer skillet to oven and roast until an instant-read thermometer inserted into thickest part of pork registers 140 °F, 10-15 minutes. Transfer to a plate and let rest for at least 10 minutes. Pour reserved marinade into a small saucepan. Bring to a boil, reduce heat, and simmer until slightly thickened, 5-8 minutes. Meanwhile, melt butter in another large skillet over medium heat. Add cabbage, apple, bay leaves, and 1 cup water; season with salt and pepper. Cook, tossing occasionally, until cabbage is softened, 15-20 minutes. Add remaining 1 teaspoon vinegar and toss to combine. Slice pork and serve with cabbage mixture and sauce.