If using Instant Pot set to saute and add ground beef and onions, cook until pink is gone, if making on stovetop do the same on low in a pot on the stovetop.
Turn Instant Pot off or leave on low on the stovetop and add taco seasoning packet, mix until meat is covered with seasoning.
Add can of black beans, enchilada sauce, and diced tomatoes and stir. Put lid on Instant Pot and close steam valve. Set to pressure high for 3 minutes or if using stovetop allow to heat up until it simmers nonstop while stirring consistently and then turn off stove and serve as directed below.
Do a quick release on Instant Pot and serve as follows:Put a layer of Fritos, then a scoop of chili mixture, then fritos, a layer of cheese, slices of avocado, a dollop of sour cream and chives on top if desired. Serve!