Pour 1 cup of water into a 6-quart Instant Pot. Insert the metal trivet into the pot.
Thoroughly pierce the potatoes with a fork to allow steam to escape during cooking. Arrange the potatoes on the trivet inside the Instant Pot.
Secure the lid of the Instant Pot and set the valve to the sealing position. Select the manual setting, adjust the pressure level to high, and set the timer for 14 minutes.
Once the cooking cycle is complete, let the pressure release naturally according to the manufacturer's instructions, which should take about 20-30 minutes.
Carefully open the lid after the pressure has fully released. When the potatoes are cool enough to handle, slice each one in half lengthwise.
Top each potato half with a dollop of unsalted butter, and season with kosher salt and freshly ground black pepper to your liking.