At least 2 hours prior to cooking, or up to 6 hours, combine the pork steaks and soy sauce in a Ziplock bag, seal the bag, and toss the chops in the sauce to evenly coat. Place the bag in the refrigerator for at least 1-1/2 hours, or up to 5-1/2 hours, removing the bag to set at room temperature 30 minutes prior to cooking.
Drain off the excess soy sauce, discard, and season the steaks evenly with the salt, black pepper, garlic powder, and red pepper.
Open the bottom vent of a charcoal grill completely. Light a charcoal chimney starter filled with charcoal. When the coals are covered with gray ash, pour them onto the bottom grate of the grill, and then push to one side of the grill. Adjust the vents as needed to maintain an internal temperature of 500° to 550°F. Coat the top grate with oil; place on the grill. (If using a gas grill, preheat to high [500° to 550°F] on one side.)
Place the pork steaks on the grill over direct heat, cover, and cook for 6 to 8 minutes per side, turning often to ensure an even sear. Remove the steaks from the grill when the internal temperature reaches 140°F. Transfer the steaks to a plate to rest for 5 minutes.
Meanwhile, in a small bowl, combine the capers, shallot, garlic, parsley, scallion, vinegar, oil, salt, and black pepper. The salsa can be made up to 4 hours in advance and kept at room temperature.
Serve the pork steaks with a generous dollop of caper salsa.