Set pressure cooker to "sear", adjust time to 20 minutes, and add oxtail. Press start/stop. Pour in enough water to cover oxtail. Allow oxtail to simmer in water to release fat, about 10-15 minutes.
When fat and oxtail excess imperfections have been released, drain the water. Remove oxtail. Trim off any additional fat remaining on oxtail.
Return oxtail to cooker. Pour in 3c of water. Close and lock lid, set pressure cooker to "meat/stew" and adjust time to 5 minutes. Press start/stop.
When done, quick release and make sure all pressure is released before opening lid.
Carefully open lid and drain remaining water.
Add cloves, bay leaves, red wine, beef stock, tomatoes, pancetta, onion, celery, garlic salt, and pepper. Stir.
Close and lock lid. Set to "meat/stew" for 1 hr, 15 minutes. Press start/stop.
When done, natural release for 15 minutes, then do a quick release to make sure all pressure is released before opening lid.
Carefully open lid. Ladle out half of liquid left in cooker.
Carefully remove oxtail, set aside. Set to "sear", press stop/start, and allow the remaining liquid in the cooker to thicken.
Chop oxtail and return into sauce in cooker. Stir and serve.
