Slice white onion; remove access fat from chicken thighs. Sprinkle chicken thighs with salt and black pepper on both sides generously.
Set Instant Pot to "Saute" setting. Add vegetable oil and briefly sear chicken on one side, the turn and briefly sear on the other side. No need to completely cook chicken. Do not overlap chicken - cook in two batches if needed.
Remove chicken. Add more vegetable oil/ olive oil to Instant Pot and saute sliced onions until they are brown and softened.
Add chicken back to Instant Pot. Then add garlic, chicken broth, Rotel (drained), bay leaf, cumin, chili powder and cayenne (omit if you want the soup mild).
Close lid. Pressure cook on high for 15 minutes. Make sure steam release valve is in "sealing" position. Instant Pot will take a few minutes to build pressure before the 15 minute timer starts.
Once done, release steam and open lid when ready.
Shred chicken. Optional: Add salt to taste to open up the flavors of the soup.
Garnish with lime (Squeeze lime to add lime juice to soup), sliced avocados, chopped cilantro, tortilla chips or other garnishes as desired. Serve and enjoy!