In a large bowl, combine the thawed corn, drained black beans, chopped cilantro, chopped red onion, diced jalapeño (if using), diced red bell pepper, 2 tsp lime juice, 2 tsp lemon juice, and 1/2 tsp salt; mix well.
Cover the salsa and chill in the refrigerator while you prepare the chicken so flavors meld.
Place the chicken cutlets in a large zip-top bag or container and add 2 tablespoons lime juice, 2 tablespoons taco seasoning, and 1 tablespoon vegetable oil; seal and toss to coat evenly.
Heat a large skillet over medium-high heat and add the remaining 1 tablespoon vegetable oil.
When the skillet is hot, add chicken in a single layer and cook undisturbed for 2–3 minutes until the bottom browns.
Flip the chicken, reduce heat to low, cover, and cook until the internal temperature reaches 165°F (74°C), about a few more minutes depending on thickness; remove cooked chicken to a plate.
If necessary, repeat cooking remaining chicken in batches so pieces cook in a single layer.
Serve each chicken cutlet topped with a scoop of the chilled corn and black bean salsa.