Turn on a multi-functional pressure cooker (such as Instant Pot(R)) and select Saute function. Add beef and saute, breaking meat up as it cooks, until browned, about 5 minutes. Remove beef and drain in a colander to remove excess fat.
Return beef to Instant Pot(R) and add onion. Cook for 3 minutes. Add taco seasoning, garlic, parsley, and chili powder; cook and stir for 1 minute. Add a dash of beef broth to deglaze the pot, scraping up any brown bits. Add remaining broth and tomatoes. Stir to combine. Mix in macaroni, stirring until noodles are completely submerged in liquid. Close and lock the lid. Turn off Saute mode.
Select high pressure according to manufacturer's instructions; set timer for 3 minutes. Allow 10 to 15 minutes for pressure to build.
Release pressure using the natural-release method according to manufacturer's instructions, for 5 minutes. Release remaining pressure carefully using the quick-release method, about 5 minutes. Unlock and remove the lid. Serve with a dollop of sour cream.
