Combine the cranberry sauce, apple jelly, mustard, crushed bouillon, horseradish, garlic powder, and thyme in a saucepan; bring to a boil.
Line a large baking pan with foil. Place pork loin in pan, fat side up. Sprinkle evenly with salt and pepper. Use a pastry brush and a small spoon to completely coat the pork with sauce.
Cook until the pork is no longer pink in the center, and an instant-read thermometer inserted into the center reads 145 degrees F (63 degrees C), about 45 minutes, basting every 10 minutes with remaining sauce.