Marinate the beef short ribs with the spices (chili, garlic, onion powders, red pepper flakes, oregano, paprika, cumin, salt & pepper for about 30 minutes
Set the Instant Pot on Saute function, add oil to pot to heat about 2 minutes, add the chopped onion, then the beef. Brown the beef on all sides. Add the tomatillo salsa. Mix and scrape bottom of pan.
Close and lock the lid. Turn the steam knob to Seal position. Select Manual Pressure cook setting on HIGH for 25 minutes (it will take around 12 minutes to reach the pressure before cooking).
In the meantime, prepare the tortillas. Spray both sides of the tortillas with cooking oil. Heat a nonstick skillet over medium high. Cook the tortilla for around 15 seconds on each side. Repeat with the remaining tortillas.
Prepare the sauces and garnishes and put in separate bowls.
When cooking is done. Carefully manually release the steam knob to venting position and let the steam to fully release. This would take couple of minutes. The float valve will drop. Remove the lid.
Remove the beef, shred it if you wish, or cut into chunks. Check the seasoning and add salt and pepper according to taste. Discard the cooking liquid.
Serve the beef short ribs with the garnishes and warm tortillas. Around 3 tortillas per person.