Step 1

In a 6- to 8-quart slow cooker, stir together the tomato sauce, chili powder, cumin, salt, paprika, pepper, garlic, and onion until well combined. Add the chicken, stirring to ensure it is fully coated with the sauce.

Step 2

Cover and cook until the chicken is cooked through and the internal temperature of the chicken is 165°F, on low for 4 to 6 hours or on high for 2 to 3 hours.

Step 3

Remove the chicken to a large cutting board. When it is cool enough to handle, cut it into bite-sized pieces. Return the chicken to the sauce and stir very well.

Step 4

Cover and cook on low for 15 minutes more.

Step 5

Serve on tortillas topped with lettuce, tomatoes, cheese, sour cream, and salsa.