If breasts are uneven in thickness, consider pounding the thicker parts to make as even as possible to ensure uniform cooking. Pat the chicken breasts dry with paper towels and rub them all over with spice mixture of your choice (I share my recommend spice mixture below). Make sure each chicken breast is evenly coated in spices/herbs.
Heat cast iron skillet over medium-high heat until very hot. Add 2 tablespoon oil and place chicken breasts in skillet. Let chicken breasts sear undisturbed for about 4-5 minutes or until they develop a golden-brown crust.
Flip and sear the other side for 3 minutes.
Lower the heat to medium-low and add a chicken broth or white wine to the skillet. If you're using aromatics, add them here, too. Cover skillet with a lid or aluminum foil and let the chicken cook for another 5-7 minutes, or until the internal temperature reaches 165 degrees. Cooking time will be dependent on how thick your chicken breast is.
Remove chicken from skillet and let it rest for about 5 minutes before slicing. You can lightly tent the chicken in foil if desired. Always slice chicken breasts against the grain.