Pat-dry the pork steaks, then dust & rub them with the garlic powder.
Mix the ingredients of the marinade together.
Place the steaks in a shallow dish (or a freezer bag) and pour over the marinade.
Marinate in the fridge for at least 2 hours, preferably overnight.
Preheat the BBQ or griddle pan, then cook the steaks for 3-5 minutes on each side (depending on their thickness).
Meanwhile, core the apple, then cut it into 5mm rings. Coat these with the pork marinade then barbecue/grill them next to the steaks.
Serve the pork steaks with the grilled apple slices.