Preheat the oven to 425 degrees F (220 degrees C). Line a baking sheet with aluminum foil.
Wash chicken breasts and pat dry with paper towels. Trim and discard fat. Tenderize chicken with a meat mallet. Rub 1 tablespoon olive oil on each breast, lightly covering both front and back. Season with salt, pepper, and garlic powder and set on the prepared baking sheet.
Squeeze juice from one lemon half over the chicken breasts. Sprinkle with basil. Cut 2 slices of lemon from the remaining half and set 1 slice on each breast. Reserve remaining lemon for another use.
Bake in the preheated oven until chicken breast is no longer pink in the center and the juices run clear, about 20 minutes. An instant-read thermometer inserted into the center should read at least 165 degrees F (74 degrees C). Remove from oven, cover with foil, and allow to rest for 7 minutes before serving.