2) Preheat a griddle to high heat. Remove the meat from the marinade and put on the hot griddle. Cook until the meat is done as desired. Transfer the beef to a cutting board and slice into 2.5cm pieces. Set aside in a bowl and cover with foil to keep warm.
3) Heat a large pan or griddle over medium heat. Spread the cut sides of the bolillo rolls with mayonnaise. Toast them in the pan, mayonnaise side down, until golden. Combine the chopped onions and coriander in a small bowl.
4) Top the bottom half of the roll with sliced avocado, a handful of cut meat, some coriander/onion mixture and some torta salsa. Top with shredded lettuce and two tomato slices. Repeat with the remaining rolls and ingredients. Cover with the roll tops, cut in half and serve.
For the torta salsa:
1) Add all the ingredients to a medium saucepan and bring to a boil over medium heat. Cook until the onion is translucent.
2) Remove from the heat and let cool. Transfer the cooled mixture to a blender and blend until smooth.