Season steaks on both sides with salt. Leave at room temperature for 45 minutes to brine. Preheat the oven to 350 degrees and preheat a skillet with oil or butter over high heat. Spray cooking spray on a rimmed baking sheet and set aside.
Sprinkle pepper on porterhouse steaks. Sear the steak on each side for 3-5 minutes until a golden-brown crust forms.
Transfer steaks to the baking sheet. Cook on the middle rack in the oven for 10-20 minutes, depending on your desired doneness. Check the thickest part of the meat with a thermometer.
Move the steaks onto a clean plate. Tent them with a piece of aluminum foil and rest for 5-10 minutes.