In a large pot, add olive oil and onion on medium low heat. Cook until onion is partly cooked, about 5 minutes. Add taco seasoning and cumin, and cook for 1 minute, until fragrant.
Add tomatoes, beans, corn, and broth. Turn heat to medium high. Once it reaches a boil, reduce heat, and simmer for 10 minutes stirring occasionally.
Add chicken and spinach if using, and cook for additional 5-10 minutes.
If desired, serve with sour cream and cilantro and sprinkle with pepper.
Notes
*I used 2 cups broth. If you prefer more broth, a soupier soup, add 2 additional cups for a total of 4 cups.
Instructions For The Instant Pot - Set Instant Pot to sauté and cook the onion. Add seasonings and scrape the bottom of the pot as it cooks. Add remaining ingredients, seal, and cook for 20 minutes on high. Let the Instant Pot naturally release for 10 minutes.
Instructions For The CrockPot - Sauté onion and add to slow cooker. Add seasonings and remaining ingredients. Cover, and cook on low for 2 hours or on high for 1 hour. (If chicken is not precooked, be sure to cook it through in a skillet before adding to the Crockpot.)
*Nutrition information does not include optional garnish.