Halve the apples and remove the core. Place skin side down in the Instant Pot. Pour the juice over the apples. Sprinkle with cinnamon, raisins, and walnuts.
Put the lid on and turn the steam release to Sealing.
Plug in the pot and press the Manual button. Select High Pressure if it doesn't default to that. Then use the adjust button to set the time to 10 minutes.
When the pot beeps to indicate it's finished cooking, allow it to release pressure using the natural method. It will take about 20 minutes. Once the float valve drops, you can open the lid and serve your apples.
As written, this has 101 calories per half apple, and it's plenty sweet. If you're not on a diet and you want to live it up, sprinkle with brown sugar or drizzle with honey or maple syrup.