Heat the olive oil in a large heavy-bottomed pot over medium heat until shimmering. Add diced onion and minced garlic, cooking until the onion is translucent and fragrant, about 5 minutes.
Add the chicken breasts to the pot and cook until lightly browned on both sides, about 7 minutes. Use a spoon or tongs to turn them occasionally, and you'll see the edges get a nice golden hue.
Pour in the chicken broth and add the diced tomatoes along with cumin. Bring the mixture to a gentle simmer, then cover and cook for 20 minutes, allowing the flavors to meld and the chicken to cook through.
Remove the chicken breasts from the soup and shred them with two forks. Return the shredded chicken to the pot, stirring to combine.
Add the corn, rinsed black beans, and chopped cilantro to the soup. Stir well, then squeeze in the lime juice and season with salt and pepper to taste.
Let the soup simmer uncovered for another 10 minutes, allowing the flavors to intensify and the vegetables to soften slightly. Taste and adjust seasoning, adding more lime or salt if needed.
Serve the soup hot, garnished with extra cilantro and lime slices. Enjoy it with your favorite tortilla chips or a warm piece of bread for a complete meal.
