Place the chicken breasts in the slow cooker and pour the chicken broth over them.
Sprinkle the chili powder, cumin, paprika, garlic powder, salt, and black pepper evenly across the chicken.
Add half the sliced onion on top of the seasoned chicken.
Cover and cook on low for 6 hours until the chicken shreds easily with two forks.
While the chicken cooks, combine the diced tomatoes, remaining sliced onion, cilantro, and lime juice in a bowl to make the fresh salsa. Stir and set aside.
Once the chicken is done, shred it directly in the slow cooker and mix it with the cooking juices.
Warm the corn tortillas and fill each with shredded chicken. Top with a spoonful of the fresh salsa before serving.