Step 1: Prepare and Marinate Chicken: Pound chicken breasts to about 1/2-inch thickness. In a small bowl, whisk together olive oil, lime juice, lime zest, chili powder, brown sugar, salt, cumin, smoked paprika, onion powder, garlic powder, chipotle chili powder (if using), and pepper. Rub this mixture generously over both sides of the chicken. Marinate at room temperature for at least 30 minutes, or in the fridge for up to 8 hours (let sit at room temp for 15-30 min before cooking if refrigerated).
Step 2: Prepare and Chill Salsa Base: While the chicken is marinating, in a large bowl, toss together the cherry or Roma tomatoes, corn, red onion, red bell pepper, diced jalapeno, cilantro, minced garlic (or powder), lime juice, cumin, salt, and pepper. Cover tightly and chill in the fridge for at least 30 minutes to meld flavors. (Can be made up to 24 hours ahead, adding avocado later).
Step 3: Cook Chicken: Cook marinated chicken using either the stovetop or grilling method until cooked through (internal temperature reaches 165°F / 74°C).
Step 4: Finish Salsa: When ready to serve, gently fold the chopped avocados into the chilled salsa. Taste and adjust seasoning with more salt, pepper, or lime juice as needed.
Step 5: Rest and Slice Chicken: Remove the cooked chicken from the heat and let it rest on a cutting board for 5 minutes before slicing. This is crucial for juicy chicken.
Step 6: Serve: Plate the sliced Fiesta Lime Chicken and generously top with the fresh Avocado Salsa. Serve immediately.