Step 1

Place onion, jalapeno and garlic in a 4-qt. slow cooker. Sprinkle roast with salt and pepper; place over vegetables. In a small bowl, mix tomato sauce, lime juice, chili powder, cumin and cayenne; pour over roast.

Step 2

Cook, covered, on low 6-8 hours or until meat is tender. Remove roast; cool slightly. Shred meat with 2 forks; return to slow cooker. Serve beef on tortillas with toppings of your choice.