Rub Brisket With Salt And Pepper; Place In A 5-Qt. Slow Cooker. Combine The Cranberry Sauce, Tomato Sauce, Onion And Mustard; Pour Over Brisket. Cover And Cook On Low For 8-10 Hours Or Until Meat Is Tender. Remove Brisket; Thinly Slice Across The Grain. Skim Fat From Cooking Juices; Serve With Brisket.