Add the red onion, jalapeño, garlic, soy sauce, and vinegar to a food processor. Blend until smooth.
Place the pork tenderloins in a large bowl and pat dry with a paper towel before coating with the olive oil. Add the jerk seasoning and use a rubber spatula to evenly coat the pork tenderloins.
Set a pressure cooker's sauté function to HI and let the pot fully heat up before adding the pork tenderloins. Cook for 2 minutes, untouched, before flipping and cooking and additional 2 minutes. Turn off the sauté function.
Add the jerk sauce from the food processor to the pot in an even layer. Seal and pressure cook on HI for 12-14 minutes with quick release pressure.
Once the pork is cooked, transfer to a bowl to shred with forks or meat claws. (You can also shred in a stand mixer with a paddle attachment.)
Add the shredded pork back to the sauce in the pot, stirring everything together. (Optional for the Ninja Foodi: Broil for 10-12 minutes for crispy edges.) Serve with pineapple salsa and warm tortillas.