Make the avocado salsa (it’s best after sitting for 10-15 minutes). Combine the avocados, cherry tomatoes, red onion, and cilantro in a large bowl. Sprinkle with lime juice and season with salt and pepper. Stir to combine. Taste for seasoning and adjust with salt and pepper.
Heat the grill or grill pan over high heat, then prepare the chicken while the grill heats up. Place one chicken breast onto a sheet of parchment paper, then fold the paper over the chicken. Use a rolling pin to pound the chicken breast to an even thickness of just under 1”. Set aside and repeat with the remaining chicken breasts.
Combine the salt, pepper, garlic powder, and onion powder in a small bowl. Stir to combine.
Brush the chicken with the olive oil, then sprinkle with the seasoning blend. Flip the chicken over, and oil and season on the other side.
Heat a grill or grill pan over high heat. Place the chicken breasts on the grill and cook for 6-7 minutes per side, or until the internal temperature reads 165°F using an instant read thermometer.
Choose ripe and firm, but not overripe avocados. Save softer avocados for guacamole.
Pounding the chicken helps to break down the tougher fibers in the breast and ensures it will cook evenly. Don't skip this step!
Always use an instant read thermometer to check for doneness when cooking chicken - 165° is just right.