Set trivet or rack in cooker and pour in broth. In a small bowl, combine onions and seasonings. Rub the spice mixture onto all sides of the pork. Place tenderloin on rack in cooker. Lock lid. Bring to full pressure. Lower heat, maintaining pressure, and cook for 35 minutes. Let pressure drop naturally for 15 minutes. Quick-release any remaining pressure. Transfer pork to a serving platter. Whisk cornstarch into the cold water until smooth. Pour into broth in cooker. Cook, stirring, until sauce thickens. Serve sauce with sliced pork tenderloin.