Start the instant pot in Saute mode and let it heat. Add olive oil, onions, garlic. Sauté for 2 minutes.
Stir in the tomatoes, black beans and taco seasoning.
Add pasta shells and broth. Stir well. Deglaze if anything is stuck to the bottom of the pot. Press cancel and close lid with vent in sealing position.Pressure cook at high pressure for 4 minutes. When the cooking time is done, quick release the pressure manually.
Add bell peppers, sour cream and cheese. Stir them well with the cooked pasta. Place back lid and let it sit for 5 minutes. You can also use a glass lid.
After 5 minutes, remove lid and garnish with cilantro. Serve topped with avocado and lime.