Add the salsa, tomato paste, and diced onion on top of the chicken.
Sprinkle the taco seasoning over the chicken mixture. If using a homemade taco seasoning, combine all the spices in a small bowl before sprinkling over the chicken.
Cook:
Cover and cook on low for 6-7 hours or on high for 3-4 hours until the chicken is fully cooked and tender.
Shred the Chicken:
Once cooked, use two forks to shred the chicken directly in the slow cooker, mixing it well with the sauce.
Assemble the Tacos:
Warm the Siete taco shells according to the package instructions.
Fill each taco shell with the pulled chicken mixture.
Top with slices of avocado, pickled onions, and a squeeze of fresh lime juice.
Serve and Enjoy:
Serve the tacos immediately with extra lime wedges on the side.