add to a large bowl your beef cubes, vinegar, lemon juice, paprika, onion powder, cumin and salt. Cover completely with cold water and cover your bowl with plastic wrap. Chill for a minimum of 4 hours, preferably overnight.
warm up some olive oil in a skillet on medium-high. Cook your onions for 5-7 minutes or until your onions are slightly charred and translucent. Remove your onions and set aside. Drain your marinated beef and add to the same pan. Cook for 7-10 minutes or until your beef is cooked to your liking.
in a food processor, place your pitted avocados, lime juice & zest, onion powder, basil, salt and coriander. Blend until smooth and set aside.
toast 4-6 tortillas and layer like so: guacamole, cooked beef, caramelized onions, coriander and a squeeze of lime.