Make your herb salt by grinding or blending together sea salt and chopped rosemary leaves.
Butterfly the chicken breast by carefully slicing through the centre of the meat and opening it like a book.
Sandwich the chicken breast between two pieces of greaseproof paper and then hit with a rolling pin to flatten it.
Season the flattened chicken breast by rubbing it with oil and sprinkling over the salt.
Heat a cast iron skillet until it is very hot. Be careful!
Put the flattened chicken breast into the cast iron and hold it down using a spatula or other cooking utensil for a few seconds. Allow it to cook 80% of the way through to get a nice brown on this side.
Once the chicken is almost cooked all the way through, flip it over to finish and seal the other side.
Squeeze over the lemon juice and sprinkle over a little more salt.
Remove from the cast iron skillet and allow to rest for two minutes. Serve the cast iron chicken breast, and enjoy!