Sprinkle the chicken with ¼ teaspoon of the salt, ⅛ teaspoon of the pepper, and the smoked paprika. Coat the breasts with cooking spray.
Heat a large heavy skillet on medium until very hot. Add the chicken and cook until well browned on both sides and the juices run clear (165°F internal temperature), 5 to 6 minutes per side.
Meanwhile, pour the lemon juice into a large bowl that will hold the chicken. Slowly whisk in the oil until the mixture is blended and thickened. Whisk in the oregano, garlic, and remaining ½ teaspoon of salt and ⅛ teaspoon of pepper.
Immediately transfer the hot chicken to the bowl and toss it in the lemon dressing until coated. Let the meat cool for 5 minutes. Slice it on a slight diagonal and return it to the bowl. Toss the pieces in the dressing and remove the coated chicken to a plate.
Add the lettuce, cucumber, tomatoes, onion, olives, and cheese to the bowl with the lemon dressing and toss to coat. Remove the salad to a platter or plates. Arrange the sliced chicken over the top.
Tip: To save time, replace the lemon dressing with 1/2 cup Panera Bread Balsamic Dressing available in some areas at grocery retailers.