Preheat the oven to 425°F. The oven should be fully preheated before the chicken goes in.
Pat the chicken dry with paper towels. Place each breast between sheets of parchment or plastic wrap and gently pound the thickest portion until the breast is about 3/4 inch thick throughout. Use a meat mallet or a rolling pin to pound the meat. If a breast is very large or thicker than about 1 ¼ inches, slice it horizontally into two thinner pieces instead of crushing it flat. The thick and thin ends should look much closer in height after pounding.
Mix the kosher salt, garlic powder, onion powder, smoked paprika, Italian seasoning, and black pepper in a small bowl or ramekin. Rub the olive oil over both sides of the chicken. Sprinkle the seasoning evenly over both sides and press it onto the surface. There should be seasoning covering every inch of the chicken, feel free to add a little more if needed.
Add the chicken breast in one layer in a baking dish or on a baking sheet. Slice the butter into 3 slices and place on top the center of each chicken breast. Bake for about 16 minutes, then check the thickest breast with an instant-read thermometer.
The internal temperature should be 165°F. If it’s at 160, I still take it out because the temperature will rise while it’s resting. So keep the thermometer in and it should climb to 165, if it doesn't, that's when you should put it back in the oven. You shouldn’t have to exceed 20 minutes of cooking time. The surface should look lightly browned, the edges should be opaque, and clear juices may collect on the pan.
Place the chicken on a cutting board and let rest for five minutes before slicing. Serve with your sides of choice and enjoy!