In a food processor or blender, blend together onion, bell pepper, tomatoes, garlic, chipotle chili thyme, allspice, salt, and pepper.
Select SAUTÉ/HIGH on the Instant Pot. When the pot is hot, add the oil. Once the oil is hot, add the blended vegetables. Sauté stirring frequently until the water has largely evaporated from the paste, about 8-10 minutes.
Add in the short ribs and another 1/2 cup of water and stir.
Secure the lid on the pot. Close the pressure-release valve. Select MANUAL/PRESSURE COOK and set the pot at HIGH pressure for 35 minutes.
When cook time is complete, let pot release pressure naturally for 15 minutes. At the end of the cooking time, use a quick release to depressurize.
Serve the ribs with the sauce on the side.
Tips & Tricks
You can use either bone-in or boneless short ribs. The cooking time will be about the same either way.
If the meat isn’t as tender as you’d like after you’ve released the pressure, put it back in for another 5 minutes on high pressure. The pot will come to pressure faster the second time since the contents are already hot.
If you want to thicken the sauce, after you remove the meat from the pot set the pot to sauté again and cook, stirring, until the sauce reduces and thickens
Macros and serving size assume half the weight of the ribs is bone so you will have 1 lb of cooked meet, with 4 oz of meat per person.