Set pressure cooker to "sear", add oil, and press "start/stop". When hot, add onions. Cook until tender. Add garlic and black rice. When fragrant, add stock (or water), sea salt, and fresh ground black pepper.
Close and lock lid, set pressure cooker to "multi grain", adjust for 5 minutes, and press "start/stop". When done, quick release and make sure all pressure is released before opening lid. Carefully open lid and fluff rice with fork. Season to taste, if necessary. Serve warm.