Place a trivet insert and 1 cup of water in a 6-quart electric pressure cooker.
Cut and discard the tops from the peppers, and remove the seeds.
In a large bowl, mix the beans, cheese, salsa, onion, corn, rice, chili powder and cumin. Spoon the mixture into the peppers, then place the peppers on the trivet.
Lock the lid of the pressure cooker, and close the pressure-release valve. Set it to pressure-cook on high for five minutes. Let the pressure release naturally. If desired, serve the peppers with sour cream.
