Dice the onion and mince the garlic; set aside. Roast the poblano pepper over an open flame or under the broiler until charred, then peel, seed, and chop finely.
In a dry skillet over medium heat, toast the cumin and chili powder for about 30 seconds until fragrant—this boosts their flavor.
Add the chopped onion and minced garlic to the slow cooker, along with the toasted spices. Pour in the chicken broth and stir to combine.
Stir in the diced tomatoes, roasted poblano, sliced chili pepper, and shredded chicken. Season with salt and pepper to taste.
Cover the slow cooker and cook on low for 4 to 6 hours, until the flavors meld and the chicken is tender.
Once cooked, taste and adjust seasoning if necessary. Use tongs to shred the chicken slightly if it isn’t already shredded.
Just before serving, squeeze fresh lime juice into the soup to brighten the flavors and stir gently.
Ladle the hot soup into bowls, then top with crispy tortilla chips, shredded cheese, and chopped cilantro if using. Serve immediately.
Enjoy the comforting aroma and bold flavors of this smoky, tangy chicken tortilla soup.
