Slice the onion and beef thinly. Trim the fat and add to a hot skillet, and allow the fat to render. Season the beef with salt and half the lime juice. Saut the onion in the beef fat. Cook the onions till tender.
Roll the beef into cigar like fashion. Slice the rolled beef across making strips. Season with a little salt, the rest of the lime juice and garlic.
Remove the onions add the butter and melt. When melted add the beef strips. Cook till liquids are reduced and beef is lightly caramelized. While that is going on take your avocado and take out the seed and scoop out of skin. Mix some salt with the avocado.
Add the onions and caramelize the beef more. Heat the tortillas. Add the avocado, sour cream and feta cheese.
When the beef and onions are cooked divide and add to each tortilla. Serve I hope you enjoy!!!!
