How to Make It
Season the steaks on both sides with the pepper, lightly patting it on.
Set a large cast-iron skillet over moderately high heat. Season the steaks with salt, add them to the skillet and cook until brown and crusty, about 4 minutes. Turn and cook for 4 minutes longer for medium-rare meat. Transfer the steaks to a platter. Pour off the fat from the skillet, add the wine and cook until reduced by half, about 30 seconds. Pour the sauce over the steaks.
Wipe out the skillet and add the butter. Add the watercress and cook over high heat, tossing, until wilted, about 1 minute. Season with salt. Cut the steaks in half, transfer to plates and serve with the watercress.