Preheat oven to 425°F. Line a 9x13-inch baking dish or rimmed baking sheet with parchment paper or foil for easy cleanup.
Place the chicken breasts between two pieces of plastic wrap or in a zip-top bag. Use a meat mallet or rolling pin to gently pound them to an even thickness of about ¾ to 1 inch at the thickest part. If the breasts are very large, slice them horizontally into thinner cutlets instead of pounding.
In a small bowl, mix together the Italian seasoning, kosher salt, garlic powder, onion powder, paprika, black pepper, and cayenne.
Pat the chicken breasts dry with paper towels. Place them in the prepared baking dish in a single layer.
Drizzle with the olive oil and rub it all over both sides. Sprinkle the seasoning mix evenly over the chicken, coating both sides well.
Top each breast with a few small cubes of butter for extra flavor and moisture as it bakes.
Bake for 18 to 25 minutes, depending on thickness, or until the internal temperature reaches 165°F.
Remove from the oven and let the chicken rest in the dish for 5 minutes. This locks in the juices for maximum tenderness.
Slice or serve whole, garnished with fresh parsley if desired.