Cook the round steak for 4 to 5 minutes per side to brown it.
Prepare the gravy mix following the instructions on the back of the package but do not heat it up, just mix it up.
Pour the uncooked gravy over the top of the browned round steak.
Put a lid on the cast iron skillet and place it on the center rack of the oven.
Bake for 2 1/2 hours, turning the swiss steak over once midway through the process. Be sure to spoon some gravy on top of the swiss steak when you do this.
When the time is up, remove the cast iron pan from the oven, carefully remove the lid watching out for steam.