Preheat the oven to 400 degrees F. Lightly spray an 8-inch x 8-inch glass or non-stick baking dish with olive oil spray.
In a small bowl, combine the garlic powder, lemon pepper, and seasoned salt. Mix to blend.
Place the chicken on a large plate or platter. Rub the seasoning mixture evenly over the chicken. Cover with plastic wrap. Refrigerate for 15 minutes for the seasonings to flavor the chicken.
Place a large non-stick skillet over high heat until it is hot enough for a squirt of water to sizzle on it. Using an oven mitt, remove the skillet from heat to spray lightly with olive oil spray.
Put the chicken in the pan, cooking it for 2 to 3 minutes per side, or until browned.
Place the cooked chicken into the baking dish, smooth sides up, making sure the pieces don't overlap. Spray each breast with 2 spritzes of butter-flavored cooking spray. Pour the lemon juice over the chicken, topping each breast with a lemon slice.
Bake for 21 to 24 minutes, or until no longer pink and the juices run clear. Remove from the oven, basting with pan juices. Let stand for 5 minutes before serving.