Put beef in a ziploc, pour the marinade, add freshly cut lime and orange. Put it in the fridge and let it marinate for 4 hours.
Set up the grill for direct cooking.
Put the beef directly on the grill grate. Sear both sides for couple of minutes. Remove from the grill.
Set tortillas on the grill to heat up. Cut the beef into small bits.
Set tortillas in a plate, top with avocado salsa, beef, tomatoes, cilantro, onion, pepper, and cheese. Then plate and serve.