To make the pickled onions, bring red wine vinegar, sugar and salt to a boil. Add the julienned red onions and allow the onions to pickle, about 30 minutes.
To make the guacamole, heat a grill or cast iron pan to medium-high heat. Place the avocados, jalapenos, onion, and lime on the grill and allow them to char. Once the vegetables are charred remove them from the grill, dice and mix with cilantro and season with salt and pepper. Mash with a spoon until it is to your desired consistency. Keep the grill hot for the tacos.
For the tacos, season the skirt steak with salt and pepper and place on the grill along with the chorizo. Once the steak has cooked to your desired temperature remove and allow it to rest, about 2 minutes. Once the chorizo has cooked through remove and slice into 1/4-inch rounds.
Warm the corn tortillas on the grill or cast iron pan, spoon the guacamole on to the tortilla, Slice the skirt steak and layer it over the guacamole, add the chorizo, cotija, chicharones, and pickled red onions.