Mix together the salt, pepper, garlic powder and ground cumin. Season tri-tip all over with blend. Optionally, you can sear the meat in a skillet over medium high heat with a tablespoon of vegetable oil if you prefer to seal in the juices.
Add the trivet to the Instant Pot pot and lay the sliced onions on top. Transfer the seasoned tri-tip on top of the onions and pour the salsa over.
Cover and seal the Instant Pot. Hit Manual or Pressure cook and set the cooking time to 20 minutes per pound. This would be 40 minutes total. Let the pressure release naturally (about 10 minutes).
Release seal and remove beef. If you find it's not so easy to shred, pop it back in the IP for another 10-15 minutes (depending, all cuts of meat may differ). Puree cooking liquid/salsa and shred meat.
Divide refried beans, shredded beef and cheese on lower third of each tortilla. Fold end closest to you up and over filling. Fold each side over center and roll up. Secure with toothpick and roll remaining.
Heat oil to 350°F in a deep skillet and fry the chimichangas in batches for several minutes each side until golden brown and crispy. Remove to paper towel lined plate and repeat. Remove toothpicks.
Serve with on bed of thinly sliced iceberg lettuce (optional), the pureed cooking liquid/salsa, red salsa of choice or Ranchero Sauce. Top with optional crema and chopped tomatoes.
I either use my Fire Roasted Salsa, or for something quick, use a 32 ounce jar of Mateo‘s gourmet salsa, or use whatever salsa you prefer.