Add onions, butter, salt, and pepper to the container of an Instant Pot or other multi-use pressure cooker and stir to combine.
Secure the lid and adjust vent to seal. Cook on high "Pressure Cook" setting for 3 minutes. Once the cycle is complete, immediately release pressure. Carefully remove the lid.
Drain and reserve excess liquid from onions and return them to the pot.
Cook over high "Saute" setting, stirring constantly, until onions are deeply golden and caramelized, This can take 10-20 minutes depending on your onions and how much liquid they have released
Use reserved liquid to deglaze and they carmelize
Optional - Add white wine and cook down again until wine is evaporated.
Remove from heat and store in an airtight container in the refrigerator for up to 1 week.
