Place the boneless chicken breasts in the crockpot. Pour in the chicken broth and add the chopped onion, minced garlic, fire-roasted tomatoes, cumin, and chili powder.
Cover the crockpot and cook on low for 6 to 8 hours until the chicken is tender and easily shreddable, filling your kitchen with smoky, spicy aromas.
Once cooked, open the lid and transfer the chicken breasts to a plate. Shred the chicken finely with two forks, then return it to the crockpot, stirring to incorporate the shredded meat into the flavorful broth.
Cut the corn tortillas into strips and add them directly into the soup. Stir well, allowing them to soften and break down, thickening the broth for a hearty texture.
Cover again and cook on low for another 30 minutes, until the tortillas have dissolved into the soup and the flavors meld beautifully.
Just before serving, squeeze fresh lime juice into the soup and stir in chopped cilantro for brightness and color. Taste and season with salt and pepper as needed.
Ladle the hot soup into bowls, garnish with additional cilantro or tortilla strips if desired, and enjoy the cozy, smoky flavor with a squeeze of lime on top.